My facetime was activated at my carrier but when I got home, it reversed to "waiting for activation", and my account was charged with a text message coming from "11447786205094" everytime I tried to use facetime.

My facetime was activated at my carrier but when I got home, the status reversed to "waiting for activation" and it stays that way for about a month now. I tried to turned the Facetime off and on, signed out of my icloud and signed back in a few times but it didn't work. I even took my phone into Apple store and have the tech activated for me, well, I was able to use it at the store but as soon as I get home, the status reversed back to "waiting for activation". Worst still, I get charged by my carrier for a text message from "11447786205094" everytime I turned Facetime on/off or used Facetime. However, the text message never showed in my iphone 5C so I don't know what is in the text message. My carrier told me that the number is an UK phone number... I verified that my phone is set up for United States. Anyone has an idea of how to fix this?