My username changed to something I didn't want!!!

Check in yout account when does the transaction happen and try to check when was the change

Then your other option is to keep the gamertag you have now.

No, the enforcement team do not have any other form of contact. The link is up to date. If it was changed by the enforcement team, that is the only way to have them review it and decide whether or not it can be overturned. Otherwise, you can change your
gamertag but you will have to pay to make the change.

You can find instructions on how to submit a case review at https://enforcement.xbox.com/en-US/home/howto#sub-topic0-6

When it changed was it because you were changing it an accidentally made a mistake, or was it changed on its own?

Typically gamertags are only changed on their own if the enforcement team issues a forced gamertag change because the tag violated the code of conduct. If that was the case, you would need to go to http://enforcement.xbox.com for
information on why it was changed and to see about submitting a case review.

The custom gamerpic feature is currently disabled. You can find information on that here - https://answers.microsoft.com/en-us...-picture/e9c0abc7-237e-48c3-9988-ae0c8294236a