You should call back and give them the RID (Receiver ID) # and the access card #.  I've gone around in circles with directv before on this as them asking for the serial # and ran into the same problem.  You can go into the sys info screen and go through step by step with the csr.  Please explain to them that there are different #'s on the unit and in the sys info screen and you want to make sure it's activated and that the card is fully functional.  It shouldn't take you more than 5 mins.