Unhappy with telkom mobile service

I have been trying to cancel a wifi router contract with telkom for 6 months now , when you call them they will always tell you they will call you back( the finance people).

Hey sold me a router that needs a telkom network coverage and in my area there s no telkom coverage 10g day and 10 g night but still they had the guts to deliver it to me and knowing very well there s no telkom network coverage. and mind you no body explained to me that the router will only work on a telkom network. I called so many times after submitting my cancellation form in november 2017 they didnt get back to me and even wrote on their facebook inbox, the gave me same old answer that they will get back to me. In 02.2018 they sent me an email with a case no that they recieved my request for a cancellation which I send in november 2017. the y are debiting my account every month for six months now for something of no use to me. In 13.03.23018 eventually they sent a technician to my house to check the network coverage, who discovered that my town phalaborwa doesnt have a network coverage. and end of march 2018 I called the customer centre to check the outcome, the consultant said that the wrote that they called me but they couldnt get me and left it like that, these people have my email adress and they should have called me again or wrote a message.

i want my contract to be cancelled and they must pay back every money they deducted from me since I submitted the cancellation form in time and I am unable to use the router since there is no telkom network coverage in my area and even this month they debited me again for something useless to me.