IMessage Suddenly changed to a different number?

Out of the blue my imessages started sending from a phone number I have never seen before. Texts still send from my number, but when I go into IMessage settings, send and receive, my number isn't even an option. I can receive texts and send them, but can only receive imessages on the random number.
We switched carriers, but this was 3 days ago, and I have not had this problem until now. I tried to reset factory setting but that did not work.
I have the IPhone 6, running iOS 8

Turn off iMessage and set it up again.

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