No connection/signal

I have been a long time customer of Telkom Mobile and I've never had major problems until recently. About a month ago I started having connection problems until eventually my modem would only register the MTN network. I'v spoken to numerous call centre agents and I've been into the store 3 times. I have done a sim swap and I've bought a new modem and I'm still having problems. I can now get the Telkom network to register but my signal is so pathetic that I can't do anything online. I am at the end of my rope with Telkom. Either someone needs to help me and resolve this issue ASAP or Telkom needs to refund me for the new sim, the new modem and the 60GB of data that I now can't use and I will move my business to MTN.