My mom can sign into att app and read my messages and she’s reading them through her phone without my permission, how?

AT&T doesn’t have the contents of people’s texts. There is no way mom is reading them through AT&T.  Texts can be saved as part of a phone backup to iCloud, but they are stored as data.  They aren’t readable through iCloud.  The backup has to be restored to a device for the texts to then be readable on that device.  About the only way for mom to read the texts would be if the texts were saved as part of the OP’s phone backup to iCloud, and then mom did a restore from that backup to her phone.  The question for the OP is, are you and your mom sharing the same Apple ID?  Or does she know your Apple ID and password?  The OP probably needs to get their own Apple ID if it’s the former, or change their Apple password if it’s the latter.

She's trying to pull one over on you.  Text messages are not available on the app.

Unless she can access your phone or if you uploaded your messages to the cloud and she knows your password, she cannot read your messages.

Ask her to show you your messages.  

I changed my iCloud password and chose the option that popped up asking if I want to sign out of every other devices using my iCloud so if she possibly knew my iCloud info will it sign her out of the app ? 

Sign her out of what app? Even if she knows your iCloud password, there is no way to read messages from iCloud. What she could do is restore a phone using the iCloud backup ant that phone would have all your messages.

AFAIK, the AT&T app does not give the user access to an iCloud account.

@formerlyknownas  I'm anxious to get your take on this situation.

@skeeterintexas You are correct, the ATT app does not give anyone access to an iCloud account. I think you hit the nail on the head in your first response, mom is blowing smoke.

@sandblaster. Sounds like Mom is trying to keep those apronstrings tied real tight!  😄

Correct on all accounts. Sounds like mom and daughter need to sit down and have a serious heart to heart.

Wouldn't surprise me if she was signed into the same Apple ID on some device. The daughter signing out of all other devices should have nipped that in the bud.

I wasn't interested in my children's text messages back in the day but I certainly was interested in their location. For that reason I did have their Apple IDs for tracking purposes. Mostly to make sure that when they were new drivers they went to school and came home again without any side trips, and that they were safe.

I have an iPhone she has a Samsung and so does the other person on our phone plan, could she get into trouble legally if she really is finding a way to read my messages. I just don’t understand how she was able to “read my messages” knowing my mom she probably would go as far as getting an older iPhone just to do that. It wasn’t the first time it happened either my grandparents did the same thing last year when I was on their plan and got my messages somehow which then I was 19 so still an adult.