Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
While it is possible that your specific phone number is ***** I doubt that a friend of yours would do so, suddenly and without any indication, on a trip to Mexico for vacation (or business) purposes.
A simple test (which also will see whether the problem is at the other end, with your friend's phone that is) is to call your friend's number from a different phone. See if it has an identical reaction... if so, the problem is with your friend's phone (or the Mexican phone system in that region) most probably, in that case.
But also: double-check your number. And, how are you dialing the number of your friend? in Mexico, certain dialing may have to be done... and, possibly, your friend's phone won't work if it is out-of-area (i.e. in Mexico.) Are you dialing the number any differently from when it is located within the United States?
And, what is your friend's phone's service provider or carrier? e.g. ATT, Tracfone, Sprint, etc.