MTN ********** transactions

MTN incorrect billing on my account A***/BA*** for self-service purchases R3477.39, I have been calling since 29.01.2021 to have this looked at after receiving my invoice for February 2021 my bill is normally R579 every month. I called MTN to advise them of the ********** transaction on my account on the 18.01.2021 with a reference number *** and still no resolution. I have spoken to many agents and the word from them is if ***** was committed on your account that’s for the accountholder to sort out. I have been an account holder for many years still with the original 083 number and this leave a bad taste I my mouth. This is really bad service I am willing to take this to court I will not be paying a single cent to that amount I will be paying may normal amount of R579 every month.