lost my account data

Changing your Xbox Live Gamertag will not cause you to lose anything. The only thing that changes when you change your Xbox Live Gamertag is the Gamertag, nothing else. Have you tried removing the account and adding it back on to your console? Have you made sure any secondary storage devices are connected properly? Are you sure you're logged into the correct account?

If you could expand on what you mean by "account data", that would help forum users narrow down the problem.

So, purchases and data from an account that will be terminated by my university will be lost?

sorry but i dont know how to remove my account whithout lost my data can you help me ?

When you start your game it should start syncing automatically. My Friend deleted all my data by accident then it synced while he was playing the restarted game and now I think I've lost my data permanently

even after resetting i jus lost all my data nd my accounts and still cant play any games at all.