My apple id is right , but when i uprade this ipad the apple shop change my apple id , wihtout my permitioan n didnot return to my original id so that i can not used this ipad freely , would u pls delette his id n using my original id :thundertwn@gmail.co

How to do now ?

When i the first time to buy tis ipad in hong kong apple store i used my user id as : thundertwn@gmail.com , but when i upgrade this ipad in saigon vietnam , the apple store change my user name become linden , without my permission also did not let me know the new pass ward so that until now i can never up grade this ipad , make me always wrong in typing the password

Whould you pls help me to solve this problem ?