Insurance Issue

I had numerous dr appts at a facility that stated they were Blue Cross/Blue shield providers when I asked them upon check-in at the first appt. After going to about 10 appts, my Blue Cross paid the 2 medical procedures they billed for, but denied the bills for the dr fees for those procedures, stating the doctor for the procedures and the other related dr fees for additional appts were out of network. Has anyone had this issue where a facility is in-network but the drs arent? They also never pre approved the 2 procedures, because if they had, they would have been told the dr fees wouldnt be paid. They also never told me that they didnt take my insurance at the facility each time I registered or tell me their drs are out of network with the insurance I presented. They also didnt send me even one bill for over 9 months, but then billed me all at once for the balances of all the unpaid dr fee bills totalling over $5500. I think I need a lawyer. Am I responsible for these bills irregardless, because I think I may need to take them to court? Has anyone else experienced anything like this? The facility would not work with me at all.