Home wifi no longer connecting to Iphone

For the past week my Iphone has been having connectivity issues with my home wifi only. If I am standing directly beside the modem I am able to connect but if I leave the room I lose connection. My internet provider is Bell and I have the Home Hub 1000 modem. I have contacted Bell and so far they haven't been able to help me solve the problem. I feel like I have tried everything at this point.