recover phone number

Probably not. AT&T cancels account entirely and phone numbers are thrown back into the pool after 60 days. It's already been more than 30 and AT&T doesn't usually disconnect till it's already been 60 days. So you're looking at more than 90 days since you went into arrears?

In any case you would have to contact at&t, pass a credit check again just like you were a brand new customer. Whether or not they can get you your phone number back we cannot say. That's between you and AT&T

Disconnected as in account cancelled or disconnected as in service suspended? If the latter, just pay your bill and service will be restored. You don’t lose the number until the account is closed. Since business accounts do have the ability to request a specific number, your chances of getting it back are better than if it was a consumer account.