MTN SOUTH AFRICA BAD SERVICE

Good day

Ive had 2 contracts with MTN one contract ended on 11 February 2023 . So on the 11 February 2023 my number was changed from contract to prepaid. Now my bill for March 2023 the contact that ended is still included im being overcharged . Ive been going to mtn stores to sort it out ive been calling 135 customer care. No benifits was recieved on the number that was changed to prepaid im only going to pay the amount due for my current contact . At this moment no one can help me