Why Wont My Phone Make Or Receive Calls Or Text Messages

I just activated my phone the other day and it just randomly stopped working. It will let me do everyting still but make phone calls and text messages. I can not receive them either. The signal bars will be full and lit up green but when i go to make a phone call the bars turn white and get very weak. I have been having this problem for the past four hours and i need my phone for work. I did everything from just turning it off for a little while and turning it back on to a factory reset and that did not work either.