Error Invalid Message - Can't Text My Mom

Hi there! @caroberk  

Thanks for posting your concerns. I’m sorry to hear you are having issues with messaging.

I’d recommend restoring to a backup prior to the 15th of April as this was when it started to become an issue.

Connecting an iPhone to a computer via USB could automatically start the backup process which would overwrite any backup created prior to April 15, 2015. If this occurs, cancel the backup process by clicking the 'X' in the upper-middle portion of the iTunes screen.

Check for last backup in iTunes or iCloud

2. If prior to 4/15/15 and acceptable, on iPhone tap Settings > General > Reset > Erase All.
3. Restore device from an iCloud or iTunes backup. (HT204184)

Hope this helps!

Charise

Unforunately Apple will just blame AT&T, nether company will take responsibility, but personally I believe it is AT&T since I just switched over from Verizon in June due to save money and never had that problem with them.  I guess you get what you pay for.

The problem is old and may be a combination of Apple and ATT.  

Solutions include:

make sure your phone is not "roaming"

delete all messages in the thread with the affected number, 

delete the contact and renter with area code and phone number.

try a test text....you phone should add a 1 only when needed for long distance.

Try a Google search for other solutions and also private message @ATTMobilityCare

click on the blue letters, then the blue message box at the middle left of screen.