MTN worst after sales service

I have been a loyal customer with MTN for the past 12 years. In Jan 2022 I was contacted by MTN's Retention department as I wanted to cancel my contract and move to another service provider who was giving me a much better deal on the phone I wanted. I was promised by the retentions department they will match the deal if I continue to stay with MTN. It is now end of July and MTN has not been crediting me with the correct Minutes for my contract. I am suppose to be getting credited with 150 minutes monthly and all I have been getting credited with is 25 minutes. I have made numerous phone call and quoted my references numbers and also sent emails to MTN customer service. To date my calls have been passed around to different departments with no help what so ever. When MTN wants your business they will call you daily but the aftersales for me has been the worst experience ever. Is there anyone else I might be able to contact to get this resolved?