Samsung S4 - Won't call out sometimes until I restart it.

[AC Question]

I have a Samsung S4 that won't call out sometimes until I restart it. Once I restart it, it functions as it should. Have not noticed what might cause it to not dial out. Just seems to happen after the phone sits for an hour or so. Don't use lots of apps and it doesn't seem to effect the ability to receive incoming calls or send/receive messages.

Any ideas on what's wrong or how to troubleshoot this?

Thank you.

Kent