[otrs] Migrate old account to new account for customer

Hi all, How can I migrate an old account to new account for customer ? Ex: I have an old customer : aa@yahoo.commailto:aa@yahoo.com and when I use LDAP authentication for customer, I sync Ldap2DB so that he has another account "xyz" . So I want to import/migrate his old tickets to new account. Please guide me how to do this. Furthermore ; It's so strange when I can't find his new account database on Mysql server , I only find his old account stored at it. Where new database stored at when using "scripts/tools/sync-ldap2db.pl" ? Although I see It uses customer_user table, but actually I can't see new database on it. Please help me to solve these problem. Best regards, Hien Huynh