Messages and phone issues on iOS6 iPhone4

I have an iPhone 4 w/ iOS6. I have had issues in the last few weeks with my messages and calls being delivered to my friends and family, their messages not coming to me, and calls getting lost in space.

Messages - First, in a group message with 4 other family members, my messages send and are delivered to all four of them. When they reply, however, everyone gets each others' messages but me. In the last two weeks my family has sent close to 50 messages to and from but I haven't been included in any of them. They all have iPhones and they all have AT&T.

I am also having issues with a friend with US Cellular (Wisconsin). I will send him messages and he won't receive them at all.

Calls - I will call people (multiple phones, multiple carriers) and they won't receive the calls but the voicemails I leave will show up to them eventually.

Is there an issue with my phone or iOS6?