MBD has blacklisted me over Virgin Active's mistake

I had two memberships with Virgin Active and had to unfortunately cancel my membership due to the fact that I had to rellocate, I contacted a representative from Virgin Active to assist with that and also assist on the amount owing. I've been dealing with the lady via e-mail and telephone and everything was sorted, my account was closed, so I thought. A month later I get a call from a debt collection company called MBD demanding a settlement on a Virgin Active account I'm owing. Confused I contacted the lady to ask her what was happening and she apologized cause she made a mistake and only sent me amount owed for the one membership and not the full membership that was xendited from one account . I then asked her if I should pay it through the debt collection company she advised that I do so. I made the payment and then contacted her and asked her to please make sure that everything is settled. It's been 9 months now and I'm still being harrased by MBD and every time I call them the amount they say I'm owing increases. Today the lady I spoke to said that every time I call them I am being charged by them and that is why the amount goes up. She in no way helped me to resolve the issue but instead all I got was attitude.

I'm so frustrated, how do you do this to people? I'm a young lady who hasn't even done anything for herself and now I am blacklisted by a company conning me into paying them amount that they won't send me no record of. Now my whole life is on hold I'm not able to do anything for myself. I'M BLACKLISTED! Eveytime I try to resolve this issue I en up at a dead end! I don't now what do!