I recently did this. I had an OC6. It took three different people on the first hour-long phone call to get that credited back to my Marriott account, with a credit of 75,000 points (the correct value). This third person on the first phone call also issued me the NC5, which was what I wanted and made a reservation for the category 5 hotel that I wanted.

However, after online review, I noticed that she debited me 135,000 points not the expected 105,000 -- she had used the QP88 rate rather than the QP91 rate (and frankly, I am not surprised, because after re-reading the WIKI, I see multiple places where duplicated redemptions for the same level of New Category partial awards have different point values). She also did not attach this incorrect QP88 to the booking, which may have been a blessing.

Second phone call, which lasted about 30 minutes: got a more knowledgeable fellow, first time around, and he successfully undid the QP88, issued the QP91 (showing as a credit for 135,000 and a debit for 105,000) and attached the reservation to the booking made during the previous call.

A few minutes later, everything looked correct in my account, and I printed copies of everything (plus copious notes from both calls)

Total time, including the original OC6 redemption back in August -- probably two hours. More than I would like, but the great value of the pre-merger travel packages made this time investment worthwhile.

Called USA been hung up 2x. Called UK been hung up 2x. 5th call on UK managed to get a very knowledgeable agent who knew the codes etc.

But would not upgrade my certs. only a straight swap. so frustrating

After 4 hours, managed to get someone on the UK line. At first she was not willing to cancel and reissue. After she spoke to her manager she managed to get it done. Total time on phone was 45mins including hold time and attachment on certs for bookings.

So to summarize, you were able to attach OC6 to NC5 for 30,000 more points. Am i reading that right? Thats what I want to do.

I have attached an old OC9 - 7 night certificate. I want to change the dates. I called 3 Marriott agents and they all said they can't call the property because it is out of cthe US, but will email. After 2 weeks, the property manager replied that I need to cancel and rebook. That of course is not possible with this certificate, as the category of the hotel has increased - now I need Tier 3-4. Do you have any advice on what is the best course of action to just change the dates and keep the certificate attached?

I take it then if I want to use an old Tier 1-3 on a new Cat 7, I can pay the difference between the old Tier 1-3 and old Tier 4-5!?

There isn't one. You either keep the dates, or you have to rebook, which necessitates converting your certificate into a new one. If you have an OC9 and it doesn't work now then your only solution to change the dates is to cancel and try to find a rep who will do an OC9 to NC7 conversion by providing extra points to upgrade.

Are there data points for this? What would the cost to upgrade be, if one did find a willing rep?

I'm in a bit of conundrum. I had a 7 night cat 1-5 TP, which was expiring Nov'18. I had called end of Sep to extend the validity and was informed by the agent that she couldn't do it at that point of time due to ongoing merger(IT issues?), but more importantly the cert would automatically be converted and extended by another year once the merger was complete.
So, I called this past Friday to attach it to a reservation and the agent said my original cert had expired and she couldn't extended it. I waited for an hour to be connected to a supervisor, but then had to hang up.
Planning to call back on Monday but thought I'll pick on the collective wisdom of FT here - am I SOL?

I am a little confused.
I had redeemed for 7 night travel packages for Category 6 (870T) and a Category 9 (990T) hotels. In my account, they continued to show unused certificates: Category 6 and Category 9 Hotels. I never converted them.
I just redeemed 7 nights for the current Category 6 hotel and the 870T certificate was canceled (used) for that reservation. Is this correct? I am not complaining if this works but
I thought the old Category 9 (990T) mapped to the new Category 6?

Thank you! I will give that a try and report back in a day or two.

Just an update. It looks like I got super lucky. My account shows 75K refund for canceled 870T and 300K deduction for the standard Cat 6 - 7 night redemption. But the super lucky part is that the difference was made up by 225K Bonus: Goodwill Adjustment. So I think the moral of the story is if you did not convert your certificate yet, do NOT convert them (unless the cert is Cat 9 or higher). Try to attach to a new booking first without converting. You can be like "I have a certificate in my account for Category 6 (or X) and want to redeem it at this Category 6 (or X) hotel". Then, just wait, pray, and maybe the rep will do the trick. Obviously this is huge YMMV.

Try to send them a message on Marriott's website. I finally was able to convert an old 5 night cat 1-5 room certificate that expired in Nov, 2018 to a new 5 night cat 1-4 cert today, after more than 2 months of back and forth.

My old cert was supposed to expire on Nov 6, 2018. It disappeared from my Marriott account a few days before. Rather than waiting hopelessly on the phone for a rep who would have no idea what to do, I sent a message on Marriott's website, asking to extend the cert.

Three weeks after I sent the message, weirdly an SPG associate replied, asking me to call because it was a Marriott cert. I was frustrated because despite using the Marriott website to send a message asking about a legacy Marriott travel cert, an SPG associate responded. Of course there was nothing he could do.

So I called Marriott in late November. The rep could not see the cert in my account because it had expired. He initially did not believe in me and said there was nothing he could do. However, when I pointed him to the 235,000 points withdrawn from my account in Nov, 2017, and the fact that I did not use any room cert in that period, he started to be more helpful. He said he would forward my case to the appropriate department. He said expect to wait 4-6 weeks for a reply.

6 weeks come and gone, and there was no word from Marriott. Not a surprise. So I sent a message to Marriott again on its website, intending to put everything into writing instead of explaining my situation to the phone rep every time I need to call. Two days later, once again, an SPG associate replied and asked me to call. This time I replied to the message telling them I did call in November but received no response. I intended to put everything in writing this time and asked them to follow-up.

A few days later, a legacy Marriott associate replied to me, saying he could not see my cert in the account. Of course I had to explain the situation all over again. This time I also attached a screenshot from my account history, showing the 235,000 points they had deducted from my account.

A few days later again, I guess a higher-up rep took my case. He gave me two options - refund the room certificate, or convert it to the new cert. I chose to convert. I specifically asked to not convert the other two room certs in my account yet. Just to convert the one that had expired in November, 2018.

This morning, I received an email from him, saying a conversion was done. I checked my account. Lo and behold, he converted one of the two certs I specifically asked him not to touch, and the expired cert was still no where to be found.

I got back to him asking him about the expired cert, saying that expired cert was all the email chain was about. He got back 15 minutes later, saying he did another conversion. This time, the expired cert finally showed up in my account.

Conclusion - it can be done, but it may take a tremendous amount of time and effort. More than one time I was going to just give up the cert, thinking it's just not worth it. Luckily, it came through after 2.5 months. I would encourage you to give it a try again, but do it in emails/messages, so you can document everything. That way you have time stamps to show your communication, and you can refer the associates to the email chain instead of explaining everything from scratch every time you call. Although I was beyond frustrated, I tried my very best to be polite. So definitely try it.

Hi: My old 1-5 cert has attached to an old cat 5 hotel. The hotel is in US and is a Cat 4 now.

I'd like to change the date, what is the best way to do it? Contact Marriott or the hotel directly? Call or email? Thank you!