Iphone not making/recieving phone calls or texts

Hello, i have a white Iphone 4 (8gb) Ios 7.0.4. My iphone keeps on going to "no service" quite a lot of the time, but if I turn it off and back on it re-connects and gives me signal. But whenever i try to make/recieve a phone call or send/recieve a text it says call ended without me pressing anything or without ringing and it says text not sent. Can you help me please as I have not had my iphone working now for 5 days? I have also reset the network settings, reset the whole phone using both icould and not using it, reset by holding home button and lock button and I have also turned my phone on and back off quite a few times as well. Can you please help me?😟