Can I Still Sue the Original Creditor Once Debt is Sent to Collection Agency?

[M3D]

I am involved in a billing dispute with a medical billing company, which sent my account to a debt collection agency last month.  Does the fact that my account has been sent (possibly sold) to the debt collection agency preclude me from suing the original creditor in small claims court if I believe that I was improperly charged?  If I decide to sue the medical billing company to resolve the billing dispute, should I also sue the debt collector as a 3^rd party defendant in the same suit?         

[Coltfan1972]

Of course you can still sue the original credtior.   You can sue anybody you have a claim against, their ownership of the debt is irrelevant.  If they violated the law you have a cause of action.   That's like if I'm involved with you in a car wreck and I later sell the car or turn the matter over to my insurance company.  You can still sue me, in fact you must.  Yes the insurance company would step in and defend but you would still sue me even if you have been dealing with my insurance company. 

[Downto0]

What violations do you think you have? You might have TILA violations if you disputed within 60 days after the billing dispute.