For those who are looking to convert OC to NC, I have just upgraded OC5 to NC5 with 60k points.
I believe I was just lucky, but here is what I have done.
- Called Australia Marriott Support line and asked to upgrade OC5 to NC5 with extra points, but the agent declined.
- Called Japan Marriott Support line and asked the same, the agent declined.
- Called US Plat line, the first agent declined.
- Then called US Plat line again and asked to cancel OC5 and order QP91 without mentioning NC5, then the agent just had it done without any further question, within 5 mins.
- Attached the NC5 to a reservation without any issue.