Hello seanyboy95,
With issues with making phone calls, start with checking to make sure your iPhone is up to date as well as the carrier settings up to date as well. Another thing to try is to reset the network settings and if that does not work then I would make sure that you are backed up and restore your iPhone. The article below will assist with all these steps if you are not familiar with them.
iPhone: Troubleshooting issues making or receiving calls
http://support.apple.com/en-us/TS3406
Take care,
-Norm G.