Bowie Health Center outrageous bill and damaging peoples credit. Bowie Maryland

Each time i visit bowie health center,despite my medical insurance (blue cross blue sheild)they always mail me some extra bills and when i call them they always say the insurance did not pay everything,that the balance is my out of pocket expenses and i always tell them to let me contact my insurance.
my insurance always say that is what they should be paid but the next thing i always receive in the mail is collection letter,and i will quicly pay them because i dont want any collection on my credit report but last week i was trying to make a purchase and i was denied,when i ordered my credit report, i was surprice to see collection on my report from bowie health center since 2007.can somebody please tell me what to do.
If you are sick for any reason,please think twice before you go to bowie health center.

Portable
bowie, Maryland
U.S.A.