Bad service

I have been a customer of MTN for more than 15 years and I am very dissappointed in them. For the last 6 months I have been trying to get a payment made in May 2020 to reflect on my account. Since today no luck, I have spoken to 6 different consultants and went in store but to no luck. Today I discovered that MTN is actually giving me a bad credit score rating. I want this resolved this month. Not happy and want to take my service somewhere else