Someone using find my iphone on my own phone?

So someone is using "find my iphone" and sending messages and sending alarms to my phone saying that it's lost however I got this phone for my birthday in January and have had it since… The message that popped up from "find my iphone" reads "this iPhone is lost, please contact me (905)-___-____" and when I try and call the number it says it's not in service or that it's not assigned… Please help! I'm not sure what to do and it's kind of freaking me out.

Try changing your Apple ID password.