Account paid but still told im owing

I had an account with cell c, I then decided to close the account so i went to their branch in victoria in pmb, i spoke to an indian lady and told her i wanted to settle the account, she then checked for me and told me i needed to pay R1900 to settle i went to pick n pay and i paid and brought back the receipt, after two or three months i received an sms stating that im owing, i went back to the shop and i was told the lady didnt tell head office that i was cancelling so they thought the money was for advance payment, we then agreed with the then store manager that the lady will have to pay the amount that was owing, which she didnt do, i ended up paying more R2900 through lawyers. I thought i was done with cell c, later on i recieved a call from another group of lawyers still saying im owing cell c, i have been to the store several times and they are failing to assist me Im really fed up with them and they are dragging me backwards.