Galaxy S5 :: Why Are Incoming Texts Having A +11 Added To Number

When u recueve a texy from someone, it puts their usual number, ex. 777-777-7777, and then adds a +11 to it, ex. +11777-777-777 It comes up as an unknown contact, and I cannot reply to that number. I tried restarting my phone, adding a 1 to the contact number, adsing BOTH versions of the number to a contact and setting the default one as the correct number, and even a different texting app. I have an AT&T galaxy s5. No root, just stock.