No Cell signal EVER!!!

I never ever have signal on my phone anywhere I go. I tried my new Samsung note 3 and my samsung galaxy s4 and had the same bad signal on both. I've contacted cell c about it. Filled in forms and sent it back. They say they have tested the signal at my house and it's fine. I asked when they tested it so I check my cctv and they can't tell me. With the new credit act I'm allowed to cancel due to a problem but cell c won't admit there is a problem. Even when cell c tries phoning me it goes straight to voice mail and I miss their calls. This is absolute nonsense.