Wi-Fi Router no coverage

I got a 24 month contract on a wi-fi router. The first few months was great. Since September I had difficulty in connecting to the internet. I phoned the call centre and they assist me to reboot the rooter. It did not help. I phoned them again. They advised me to do a sim swop which I did. No success! I phoned again and they checked coverage and told me that I have very weak to no coverage and will have to cancel the contract. I went to the Telkom store in Wonderpark Akasia. What a bunch of unpleasant people!! After waiting for 1 hour they gave me an application form and logged the case. I waited 1 week and contacted Telkom. After another week the IT guy came out to test the coverage. He also told me that there is no coverage. He explained that initially I had coverage but the tower in my area had been vandalized and they can not pick up a signal from the other tower for it is too far. He would put in his report. After a week I had no reply and I contacted Telkom. They sent another IT guy. They tested and moved the router around and eventually told me the same story. They checked weith the office and confirmed that the tower is still out of order and will not be repaired any time soon. I contacted Telkom again and required cancellation immediately and requested a refund and that the debit order be cancelled. I got a reply from Telkom saying that if I want to cancel the contract I will have to pay an early cancellation fee plus the remaining months of the contract which is 6 months. On the same day of their reply the debit order went through my bank. I immediately reversed the debit order. My question is.....how can they breach the contract by not rendering the service but I have to pay. I have been paying already for three months without receiving the service. However they claim that data has been used. I wonder by who because the router was switched off since they told me I have no coverage the first time. Are there more people who are having difficulty with coverage. Regards.