MBD RUDE AGENTS

I cancelled a cell c account and queried what my outstanding balance was and was advised that my account balance was nil....I understand that you need to give 1 months notice and was fully aware that I would owe cell c for the final month - After following up 2 months in a row with cell c I was assured that there was nothing outstanding on my account - I then received a sms from MBD and tried calling them on the number provided and eventually got through and they said that they were having high call volumes and to leave my name and number and they would call me back - No one bothered to call me back. I went in to cel c and requested a balance of my account and was then advised that I owed an amount of =_ R328.00 which I then paid directly to cel c and sent a email to cel c with the proof of payment and advised that it was in full and final settlement of my account. I received a email from cell c thanking me for the payment. This morning I receive 3 calls from MBD offices and 3 x I had the call put down by the agents which I feel is extremely rude - I was advised that another R71.80 is due - I do not OWE anything on this account and requested that they remove me off their system - In my 62 years I have never come across such rude call centre people as the ones that are employed by MBD.