I was contacted end of February 2025 by their sales person and she sold a Data Similar deal as a loyal customer (more than 10 years with MTN) and that I was due for an upgrade on the current line

I was contacted end of February 2025 by their sales person and she sold a Data Similar deal as a loyal customer (more than 10 years with MTN) and that I was due for an upgrade on the current line. Only to find out she added a new line on my name. The device (mifi router) was part of the deal. I returned the package to Secunda Mall branch in good condition and followed the cancelation procedure as Mtn instructed. In March I was debit about R600± for the cancelled line, April debited again about R1000± for same line (Reversed all debits). In between I reported to them with emails and the branch also couldn't help me on this matter. Last month May 2025 my credit record showed me I owe MTN R520 need to pay and today 28.06.25. I received an sms reminder to pay cash R1922.68 for the same canceled line. I do not own the device and the data line I am not using it. However I am tortured and my name is included on the credit bureau for an account ...7455. I dont know what to do, anymore.