Account in a minus

I did a migration at the end of January 2020. I had to call them almost everyday to sort out the migration because I got the wrong data and the package I was put on was also wrong. I did not know how they do their work there. My account was deducted last month for data I never agreed to. After that my account was fine. Today, the 12 of March 2020 I got the correct data, however my bill is now showing I'm in a minus of R-959.23 why? When my payment is R299 which I agreed upon when the migration was done in January already. Something does not add up. This is highly annoying, and I regret deeply for doing this migration with MTN and even taking a contact out by them. Please enlighten me to why my account is in a minus, because I can guarantee you, I'm not going to pay for something that I not my fault. I need a decent person to sit behind their desk and sort out this garbage.