iphone makes random outgoing calls to non-contacts

Since about 9:45 this morning, my iPhone has been making hundreds of random calls to numbers I don't know. My voicemail is now full. I have received 100+ text messages that are turning nasty. Any ideas on what I can do?

I have had AT&T turn off service so, in theory, I cannot make or receive calls - I have tested and this is true, BUT I am still receiving texts - "Who is this" "I will call you later" "I am in class" "Sorry I can't talk right now". I have received call backs from all over the US. English, Spanish and even Japanese texts.