[otrs] changing customer id loses customers tickets

Hi, Is it intentional that if you have an existing user with tickets that if you change the cstomer id that they appear to have no tickets associated with them the next time they log in. if you change the customer id back to its original value then the tickets reappear. I am guessing that this is relating to the customer_id value in the ticket table. If I wish to change the customer ids in use can I just ho thru the ticket table and change the customer_id to the new values and the tickets should retain their association with the user? Now going back to read the docs again :) thanks