MTN dissatisfied customer. Is MTN *********** ??

I have a sky package with MTN and 10 gigs of anytime data per month. Their system has changed it to night time data only which is not what my contract is. I have logged 4 tickets and each time they cancel my ticket number without resolving the issue, and I have been into 2 branches to try and resolve the issue. They has not been able to fix the problem. I have been a loyal customer since MTN started which is more than 20 years. My account is always paid on time and I’m fact it’s is in credit. What are my next steps to get service from MTN