Data contract cancellation

It is very disturbing to deal with untrained or poorly trained staff members. MTN is really unprofessional with the way they handle their cancellation process. Their staff member was not able to cancel my data contract and they continued to bill me right after I had cancelled. They are now handing me over to debt collectors. This is really unacceptable because it will ruin my credit record. I have been dealing with this since 2021 and they last said they will investigate the matter. To this day they have not. I am not going to take legal action against this unfair treatment.