Existing and New AT&T wireless services customers
The common message center number provisioned on all AT&T SIM cards nationally is +13123149810. Multiple Message Center Numbers are available for each region; however, each will function the same regardless of what is chosen. If there are problems using the national message center number, please contact AT&T Customer Service for wireless customers for an alternate number.
Former AT&T Wireless Customers
All former AT&T Wireless Customers use +19703769301 nationally.
IMPORTANT: A plus "+" sign MUST precede the 11-digit message center number in order for SMS to function.