MTN BUSINESS BILLING ****!

I have a business account and one of my lines is Made for Business L R579pm for 23GB data and 1000minutes. This was going on fine for many months, until May's invoice which went up to R2128.23. My new account manager Thola Majozi cannot assist. My previous account manager Divashen Pillay says I must wait for Thola. My requests for this explanation fell on deaf ears. Thola guessing and said it was my upgrade (which was NOT done), then its a dual sim (wrong again), then its credit not passed. Credit was passed, however there were duplicate charges, which she failed to see! She emailed me saying credit or R500 is pending approval to be credited on next statement! I was overcharged R1549, yet a credit of R500? I did NOT budget for this and cashflow is restricted with lockdown! Calls to her are unanswered.