Over charged monthly for contract & line suspended

I did an upgrade with MTN last year November, and paid my contract to cover fees for December also, hence i ddn't pay in December. Come end of Jan 2016, my line was suspended and I received a statement that i owe them up to R 392. They claimed that I've been owing them since November and never paid. I have proof that I paid, but since I was desperate and wanted my line reactivated, I comp**** to their silly and ********** claims, and as if that was not enough, my line was cut off about two days down the line, stating similar claims and yes they wanted more money! That drove me insane.. Recently I lost My fone and had to phone their inefficient service desk to have my phone blacklisted up until I claim back my phone from my insurer. Yesterday I went to one of their branch in Pretoria in state Theater building. I paid for the sim card by the way (R140) which is upsurd, when other service providers replace them for free! Then the service desk agent told me they can't reactivate my line since I owe them R175, and by the way I phoned the 808 number to have my line reactivated the previous day, and the agent confirmed that it was active. Only to find that I still can't do the sim swap!