They blocked my Sim Card

Good day<br> <br> I am so angry I don't know where to begin. I have been sending emails to MTN customer service since early this year to get them to change my method of payment to Cash which they only did in July. The last deduction they receive from my bank account was in May, I made a cash payment on June because I knew they would not receive any money on Bank Account, which they took almost 30 days to acknowledge my payment for, the threatened to suspend my account but later send an email to apologies for the error and assured me that my account was up to date I then made another payment end of July for July premium which they are also now refusing to acknowledge to the point now that they blocked my SIM CARD. they are saying I owe over R600 which is incorrect I have all the proof and transaction showing the opposite, now I can make calls nor use the Internet, I know from my side the only amount outstanding is for August which is still due until the end of the month because I make payment month end. I have send emails sine yesterday sending proof till now they have not responded to any of the emails sent to them.<br>