how to get the cell phone code

 
For my contact information there asking me for my mobile number so i can use it to purchase things as proof its me, but whenever I put my number for them to send me an sms confirmation, I don't get anything. And my number is right, trust me it works, and I'm doing it right. I tried it many ways as well. I tried it 6 times six different ways. Can someone please help me. I live in the U.S.A and my number is +1 267 4235010 and that's how i typed it into the mobile box thing they want us to type it in. 267 being the prefix. Anyway, I don't understand why they just didn't have one use there email as a confirmation. 
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