Supersonic F-LTE Unusable Network Speeds between 19h00 and 22h00

For the past 2 weeks, we've been experiencing super slow network speeds between 19h00 and 22h00 (ping/latency of 500+ ms and download speeds below 1Mbps). I've called Supersonic every single night, having to hold in the phone for average 20 minutes, using more than R1200 worth of airtime. Everytime they say they will log the issue with the technicians, but I have only received feedback once. I have to pay R999 a month plus airtime usage for this fixed lte service and I can't even use it when I am at home to watch a series, or play some online gaming. I would like this to be resolved or rather get this service canceled as I am paying over and above for something I can't use when I am at home after a full day of work.