Poor financial service from MTN

On 15/06/2020, MTN suspended my service for 4 days, stating that I did not pay. I have paid on the 2nd of June and have forwarded a POP on the same date, which was confirmed by MTN on the 2nd as received. It took 6 more POP's before they restored my service on the 18th at 17:40. They also double debited me for my monthly service package of R 607.83 plus VAT, on 26/05/2020 and on 26/06/2020. After numerous phone calls, and emails the responded on 26 july that they acknowledge the mistakes and have passed a credit. Upon receipt of my statement today, I have noticed that they have credit my account with R 1398.01, which is the correct amount, but my opening balance balance as per my statement received today is R6917,81, compared to the closing balance balance on my June statement of R 5508.30. This is a difference of R 1409,51. They have recharged me for the credit they gave later. This is pathetic service from one of the biggest Quoted Companies in South Africa.