In my admittedly limited experience, I've had good success with actually talking with a person at the OC after contacting them by mail. Yes, I know that "never call" is usually said about CA's, but the OC (actually the medical biller for the OC) was relatively easy to work with from my end.
What worked best for me was sending off a letter CMRRR first, then calling to confirm that they actually understood the full series of events/timeline/insurance foul-up. It resulted in an AUD (automatic deletion) for me last week, after about 6 weeks of "dealing" with the issue.
YMMV....
atlast...still waiting for it to drop off of TU...
Ficos 2/17/08: TU 551 EQ 534 EX 587
Ficos 2/12/09 TU 695 EQ 715 EX 715
Fico...4/15/10....drumroll.....EQ 743