My phone won't let me receive or make calls or text messages. I've contacted my carrier and my sims working fine and I also bought a second son incase and they both work fine in other iPhones. It says call failed when I try to call

my phone has been doing it his ever since around February. It won't let me make or receive calls or messages. I've contacted my server and bought a second sim just in case and they work fine in other iPhones. It says no service (Even Though every one else does have service) and sometime only shows 1-4 bars and even then it won't let me make or receive calls or messages. Please help me I don't know what to do. I've re inserted the sim many times, I've switched on and off and ive put it on airplane mode and everything. And also I've moved since I bought this iPhone meaning I'm in a different country. I