Poor service

In January 2019 I received a call from MTN consultant offering me an update for cellphone J8.I told the consultant that I like Huawei P30 and he told me that I cannot afford it,I agreed to take J8, I also told the consultant that I am not receiving any benefits from the existing contract because I didn't receive sim card,he told me that he is going to credit the benefits to my prepaid number ***. Following day I changed my mind I decided to cancel the upgrade because I didn't like the J8 after I saw it on internet. I sent an email to MTN to cancel the upgrade.

In March I received an notifying me about an overdue account ,following I received another nofication about overdue account again,until June whereby I asked them about my instalment they told me that it's zR600 and something. I asked them how come. They told me that I made an upgrade in January 2019,I told them that I sent an email to mtn cancelling the upgrade. The response I received them was that the upgrade was made by external company,they told me that I can contact the company and ask them about the upgrade.

The query for sim card that I did not receive is not resolved it's been a month after I logged the query. My prepaid number ***has been blocked,all the services are terminated.I can't pay for services that are not rendered to me. It's MTN's responsibility to investigate and tell me what happened with the upgrade,why they're are charging me for cellphone that wasn't delivered to me. And now I'm receiving payment notifications that my account is overdue. I am not going to pay for services that are not rendered to me.