there are some limitations. the carrier must be a trading partner with cricket. the list is pretty extensive, but i can't find it right now. MOST carriers including pre-paid are partners with cricket.
EDIT: Also the nuraber must be a local nuraber to the cricket market where the account resides. or if it's in a different cricket market you'd have to make a new account under that market. #'s that are local to an area not covered by cricket, cannot be ported onto cricket service.
