Ooops we are sorry about that. Please see some reasons why messages may not deliver. 

UNDELIVEREDYour message was not delivered. This happens when the Carrier encounters
  1. inactive or unidentified or untraceable destination mobile number
  2. mobile handset memory or inbox full
  3. no credit balance is available to receive the SMS Text message (specifically for pre-paid or pay-as-you-go)