POOR Telkom internet service

I signed a 24 month internet LTE contract with Telkom middle August 2019. Although I fall in the middle of the coverage area (500m from the closet tower) my signal is only 3/5 bars and my speed during the evenings barely reach 3Mbps, it sometimes drop to below 1Mbps. During the daytime it also fluctuates a lot. I was told by Ganoly Shandre Robby from Telkom to change some setting on my router and reboot it (will that help to increase the signal strength ???) NO CHANGE. The local Telkom Shop (Mall of the North) is not helpful at all. the issue need to be resolved since I pay R899/m for NO service. If Telkom cannot fix the problem I am going to cancel my contract