I dont know if they do this any more, but if you have one carrier and your friend has another, your friend's carrier reroutes the text message number to an assigned texting number under their carrier so the text can go through. The end result is your text shows up as a different number or your friend gets billed twice for it. It was a real mess at one point for a lot of people.
I sent a couple of text messages and people were asking me who I was because it showed on their phones as Montana...which is not my name and this is not my number. Why did my texts say they were from this phone number?
I dont know if they do this any more, but if you have one carrier and your friend has another, your friend's carrier reroutes the text message number to an assigned texting number under their carrier so the text can go through. The end result is your text shows up as a different number or your friend gets billed twice for it. It was a real mess at one point for a lot of people.