cellphone Contract Dispute with MTN

I have a contract with MTN did renewals more that 3 times. In December 2023 made a renewal of contract ,still using same package with new devices. I noticed that in February that when data is loaded it finishes within a day and a half. Managed to top-up but it made no difference. This did not bother me since most of the time I used data through WIFI at home. I tried to log call with MTN call centre but they had a network problem. Later i realized this is accumulating then i called East London - Beacon Branch since its the branch that i used but could not get anything tangible.They said i must go physically managed to go to King Williams Town Branch that is closer to my work but then they said i must log call with call centre to arrange this payment, even though my dispute with bill but there was nothing tangible. This week I've written e-mail through their customer care and ***** unit nothing . Instead this is making a bad impact on my credit profile because they are debiting unpaid amount that i don't have.

Kindly assist with the matter