freak, it is NOT true that you can't get credit for your MCI service. your agreement with MCI is that you'd receive miles as long as you met your part of the agreement ie, length of service, etc. as long as that's the case you CAN go back and get your miles.
i had to send a complaint to my state's FCC, and within a week all miles posted. and my service had been discontinued three months prior to the deposit of miles.
don't give up yet!