Wifi not wifing

I bought a router at Telkom and it doesn't have a signal.its been 8 days now and we cant watch any show after 6pm.The signal is so bad that we have to sleep early because our Tv isn't on.I went to the store and the told me that there is nothing wrong with the it,its just a signal problem.But the problem is i will have to pay month end for service that i did not receive .why would they sell it to me if they knew that their network coverage is not covering my erea,They have my address,so why not tell me that my location won't be covered .Its unfair that at the end of the month for the next 24 months,i will be paying for something that it is with no use to me and my family.