PLEASE SOMEONE HELP! iphone 4s problem, 10 POINTS!!!!?

Ive had my iphone 4s for about 7 months now, and i updated my phone to iOS6 about a month ago, or something like that. 2 days ago, i found that whenever i rang someone, the call would fail. Its not with only one contact, it happens with all of them. i really need to make my calls but i cant because whenever i try to call someone it just fails! Also, when people try and call me, it doesnt go through to my phone, so i cant see if someone is trying to call me.

ive looked up some solutions on the internet, and NONE of these have worked:
-Turn 'Airplane Mode' ON for about 10 seconds, and then switch it back off, and now see if the phone can make calls.

-Go to Settings > Phone > Show My Caller ID. Now just wait for it to load.
 
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