Here is the at&t sms short cdes for quick account updates
AT&T data usage number(internet data usage)
*3282#(*DATA#)
AT&T remaining minutes balance
*646#(*MIN#)
AT&T upgrade eligibility check
*639#(*NEW#)
AT&T gophone check balance
*777#
AT&T Account balance ( next bill due date, last payment received )
*225#(*BAL#)