Would like to know what gamertags is associate to my mail

Each gamertag can only be associated with one mail email address.

Only phone support would be able to assist in this matter. Please let them know you are trying to find out the e-mail associated with your old account. Let them know the gamertag (do not start with giving them the e-mail as you might be giving them an e-mail
that is not working correctly or is disconnected in some way).

Once you are able to verify the information that was on that gamertag they should be able to read you out the e-mail associated with the account. They should be able to see what accounts are associated with what e-mails.

You will need to contact them again.

This does suggest Microsoft account is associated with the wrong email. What I would do is on the Xbox with the Gamertag you believe is the right one is check the E-mail address associated with it. A Gamertag is associated with a Microsoft Account but
the E-mail address that is associated with a Microsoft Account\E-mail address can change. Hope that helps and makes sense.

If you know your information like e-mail and password associated with the account then try to recover your gamertag.

It actually sounds like your account was compromised and they changed the e-mail address associated with it. What was your old gamertag?