Hello,
you don't really need your account info (email adress and password on our online portal). All you need to do is call your avast! PIN like you would do with a phone number to open Anti-Theft.
If you don't remember the avast! PIN, I would open my.avast.com in a browser and use the "forgot password" option to retrieve your online password. just try all your email adresses.
in the portal you can mark your phone "found" and change the avast! PIN aswell!
regards,
Werner