MTN STOLE MONEY FROM MY ACCOUNT

I went in for a sim swop. They changed my contract to an open contract without limits. I know have a R 3 000 bill. Its impossible because I use my wi-fi at home.
They send me a bill but it doesnt make sense. MTN is also not coming back to me. I've spoken to at least 10 people and no one can see whats going on. Now I am inconvenienced cause I have to go to the branch to be authenticated. I am sure the lady who did the sim swop caused this havoc. This was in November. I didnt authorise for the contract to be an open contract. I do not qualify for a upgrade or cancellation. Who CHANGED my contract? This is ***** - you cant just take money from my account. I stopped the payment at the bank otherwise my debitorderes wouldn't have gone through. I has now received a sms telling me I must pay the R 3 000 and that they are putting a hold on my phone. This is not my doing MTN MADE AN ERROR! My contract for my 2 phones are inclusive R 600 for the 2. Can someone who knows what is going on please call me on **********. This has become ridiculous now. I am beyond livid. MTN YOU ARE AT FAULT ********** zero one zero four nine five five double zero six. zero eight three seven eight nine sic three zero three GF CARR