MTN Billing Mess

I was on contract since Oct 2015. I was billed a promo service fee for my iPhone 6s. When the contract ended in Oct 2017 i did not upgrade but continued on a month to month bill. The promo service fee was cancelled on my account. In Sept 2018 I went into the store and migrated my package to a smaller package. I did not do a upgrade nor did I get a new phone but on my account for Oct 2018 I was billed a promo service fee as if I have taken a phone and upgraded my contract. There is not one person that seem to be able to resolve my problem at MTN. Tickets gets logged and closed with no resolution.