It is from "74611888" and it says: "Free Message: AT&T AllAccess activated - learn more at att.com/allaccess xxxxxx-nnnnnn"
The x's are random numbers and n's are random letters. I assume it is some sort of validation message but somehow it must be stuck. I got the same message the first day I got the phone (a month ago) but none since then until the update.
Any ideas on what is happening?