We received a call from the TA and I have read that this method is very common. Some people have just received their documents with a room number assigned and the catagory was a catagory higher than they booked...I've even heard they find out at the port...
don't forget, many of us need to look up the room number to see the catagory so sometimes it isn't obvious...when my TA called (not a great TA) she was concerned I be upset that I had a different room - she didn't know it was an upgrade
Barb