Worst service available

It's now been going on for 90 days maybe more. I have excellent A-LTE speed during the day but during the evenings it's unusable. I'm not in a big city that they can say it congestion on towers. Plus MTN did send their engineers to my place and checked everything. My MTN LTE works 100% day or night, while using the same towers. No one at Supersonic has made any effort sorting this problem out. All while I'm on their premium LTE package.