Cant make or receive calls after updating iPhone 4s iOS 9

I have a iPhone 4s and I recently updated to iOS 9. Since updating I cannot make or receive calls. When I make a call it simply beeps 3 times and returns to the previous screen. When I try to call my phone from another it rings once then get a busy signal, once in a while it will go to voicemail but the busy tone is most common. I can send and receive both iMessages as well as text messages, as well as use the internet and all other applications without any problem using cellular data. I have tried troubleshooting by power cycling the phone multiple times, turning airplane mode on and off, turning Do Not Disturb on and off, pulling out the SIM card and placing it back in, and resetting the network settings. I have read a few things online where some users have had the same trouble, did the same troubleshooting and even went further by completely resetting the phone but that didn't resolve the issue. Any other suggestions? It's really hurting me not being able to make and receive calls. I rely on my phone for work/income, needless to say today I lost out on that. Its really important that I get this issue resolved before going to sleep tonight. Thanks!!