Perthitic service

So MTN is a real ****. I paid R1000 on the 29 July and was left with R1131,25 to settle my account in full. I then get a call from mtn in the beginning of August stating I haven't paid my account and they don't pick up the R1000 payment I did. Mtn then forces a debit order of R2063.85 . so the R1000 i paid was me donating it to mtn. This is so perthitic. Mtn must just fix this mess