MTN bad service.

Hi, I took a contract phone at MTN Zewenvacht Mall on 28/10/2020 and I was assisted by a lady called Ntombodidi. After a month I received my statement with a balance of R2500 and I was shocked and went back to the store and assisted by a guy called AYANDA who had a very very bad attitude so he could have prevented this. Now on the 5th of November I received my statement again and the amount that MTN claimed that I owed them was R4800 so I immediately called their call center but still I did not get hold of anyone , but I kept on trying so eventually after few days they answered the phone at call Centre. They checked my account and told me that my contract is an open line account which I did not have any clue about it and I asked the lady that was assisting me to explain more about it and said I need to go back to the store not to any MTN store other than Zewenvach Mall store for this. I went back to the store and asked for a manager because now my phone was suspended I could not do any calls or anything on the phone, then paid R1000 for September and October because I have signed for a contract of R499 per month. All in all MTN says I must pay the R3800 balance and I still believe that it was not my fault it was their consultant and their system and what I am worried about the most is that this is going to affect my credit record. I will now log a complaint to ICASA ombudsman.