Account

Mtn send sms to my phone on 15 Jan 2016. Stated that I have exceed my limit of my account. The limit on my account is R1600.00. They block my phone. After phoning the customer care centre they said that my account is already R4600.00. But they will unblock my phone. They couldn't explain why did they let exceed the limit. After phoning a second time they hangup on me why explaining. After the 3rd call they say it is on my 3G of which I an having a limit of 2GB and according to me on a Topup. But in Des 2015 they invoiced me for R590.77 for Packet Switched Data Calls. Needles to say I only received my December account on the 8 Jan 2016. I visited a branch in Polokwane today 16 Jan 2016 and they too couldn't give me any explanation. They also phoned their customercare centre and they just say they cannot help. Then the lady at the branch send a email to the admin office of mtn and said that may be they will have feedback by Monday or Tuesday. But no one can explain to me how is it possible that if I am having a limit of R1600 how is it then possible that I can exceed it. I am not in the financial position to pay this amount and also not prepared to pay any thereof. Please help.