MTN ONLINE

I got a router from MTN Online and it didn’t work, it had no network coverage. I reported the matter to them and they said their agent who sold me the contract was supposed to check my location first of which she didn’t. I called again to try and cancel the contract because they were billing me every month for a router that is inactive and they kept transferring me from one agent to another until one brave agent hangs up on me. I wrote MTN Customer Care an email explaining my problem and the response was a billing letter.I then went to the MTN store and they said I should cancel my contract online and they gave me an MTN Landline number which I called and as soon as I explained my problem to the agent who took my call they hang up on me again. I tried calling again a few minutes later and no one was picking up. I am in need of assistance to solve this matter.