I can't link my number to my iMessage.

I'm a Peruvian resident, and I live in Peru. Last week I went to Washington D.C. and my iMessage started crashing as soon as I got there. I restarted it, and it activated but not 100% perfectly, my phone number wouldn't appear on my 'Send & Receive' options. I reseted my phone's settings twice; once when I was in Washington D.C. and once when I got back in my country. It's been almost a day since the last time I reseted my phone, and it's not working until now. I wonder if any of you have the same problem. I really need help.

PS: I can link my email to iMessage, but I'd prefer to link it with my phone.

PSS: The same problem happens with FaceTime.