How to remove additional 1 when sending SMS

Everytime when I tried to send a message, for example to (XXX)XXX-XXXX, when I sent, AT&T always return to me and said the number "+1(1)(XXX)XXX-XXXX" is invalid. I've never add an 1 before the number and I've tried some other number, it still happen. I guess that the iOS will automatically add a country code before the number, and without a plus, which AT&T's system cannot recognize.

Do anyone know how to have the iphone stop this or any other solution? Thanks.