Earlier this year I booked two CO flights for my wife and me --- one for Sept and the other for Nov --- using my $99 companion certificate for one flight and my wife's for the other. As per the CS's instructions, I mailed both certificates (the originals, since photocopies are not accepted as per the certificate instructions) and the Flight Confirmation info to the Houston address she gave me.

I kept checking my On-Line OP Account data month after month, not seeing anything to suggest receipt of the coupons. I probably made five or six calls to Elite OP Line --- and got the same response each time: the booking was preserved but the certificates had not been received so no confirmation for the discounts was entered. Each of the CS reps told me that they were able to see the content of my previous telephone calls --- but there was nothing they could do. I finally wrote a letter (using gentle tones, not an angry assault on CO) to the OP Service Center expressing my frustration, and I included photocopies which I had originally saved for my own records. Finally, someone at CO OP took pity on me and actually called my cell phone to tell me it had all been straightened out --- and indeed it was.

Lessons learned: (1) either do not ever use coupons/certificates with CO or make lots of photocopies before mailing the originals; (2) use Registered Mail with Return Receipt Requested. At least if the Return Receipt comes back to me, I will know that OP, not the USPS, lost the paperwork.

By the way, my wife and I got 100% EQM and we were upgraded with FF Miles as well on both the regular and the discounted tickets.