Att.net email

AT&T's policy is that if your closed Internet account is in good standing (i.e. no balance due, no unreturned equipment), that the e-mail address is turned in to an "AT&T Free E-mail Account" and you can continue to use it indefinitely.  Be warned that what little support you might get for e-mail as a paying customer will be gone when the price is free.

Can you direct me as how I turn my current account into the free account? Thank you ! 
I don’t pay anything now for the email.

There is nothing to do (other than end your paid service).