MTN customer service sucks

I have been a client of MTN since 2020 when I took out my first contract. I have had no problems until November 2023. I pay my account in-store or via the APP every month and have never missed a payment. In September 2023 I did an upgrade and changed my payment method to debit order, but I still made payments in-store as normal. No debit orders came off in September and October. In November I paid R6500 which was my outstanding bill. MTN then ran a debit order of R1600 two days after my in-store payment. Two days later in November, they tried to debit my account with R4800 luckily I had no funds in my account. When I called 135 they told me a refund would take up to 21 working days as I requested my R1600 to be refunded. to date 16/01/2024 no call back and no refund. I had my payment method changed in-store from debit back to cash. When my payment method was changed my payment date and period were changed on the system without my knowledge consultation or permission. My Bill Run was from the 12th of the month to the last day of the following month. In December my Bill run was changed from the 12th of the month to the 2nd of the new month. I did not request this change and I have been into the store they have logged a ticket after 48HRS the ticket was marked completed, but my bill run was not corrected. At the end of December, I paid my account on 02 January my account was suspended because of this error on their system. I have followed all the channels and it has not been corrected. I had to make a payment arrangement because of their system issue just to be able to use my cellphone. This error now means that I will be in arrears every month with this account and that every month I will need to make a payment arrangement that affects my Credit Scoring negatively and causes me unnecessary suffering. I am strongly considering moving all 4 of my contacts to a service provider that values its customers and assists them in fixing errors that are costing them money.