I got an upgrade about a week ago, a sprint viper. It was functioning fine until yesterday when it suddenly stopped making calls. Everything else still works fine, internet, text, apps, everything. But not my phone. When I dial a number as soon as I hit call it hangs up. No matter how many times I try, it won't call out. I don't have a house phone, and I have no way of knowing if I can't recieve calls either. I haven't gotten a call since this started. I need to know how to fix this, pronto!