Disgusted by stale accounts

Got 2 letters from Medicross. 27/06/2014 for R284.60,found proof is was paid 10/07/2014. Said they will check & a further R700+ is due for 27/05/2015 & 09/07/2015 medical aid didn't pay.Called my medical aid again, was informed they never received those accounts. Called Charmaine back and asked proof they submitted to medical aid. She said she'd get back to me,never did so I called today& she said she is sorry,her manager says I am liable for the accounts. I consulted and made payments to them after these dates for levies and was never told about problems with submissions otherwise I could have submitted to the medical aid myself. I still had a lot of benefits at the end of the year that I now obviously can't claim as it's a new year and also there is no proof that Medicross even try to submit the claims. Strange they had problems with healthbridge both occasions but nothing to show. They should take responsibility. I'm sorry i only started working here recently & my manager says is not acceptable. If the manager was on top of things there would not be this problem. No apology for threatening to hand me over for 2014 account that was paid. Disgusting.