The same way you recover any other deleted data for which you didn't make a backup: you don't. You eat the loss & make new accounts. Then you remember to make a

The same way you recover any other deleted data for which you didn't make a backup: you don't. You eat the loss & make new accounts. Then you remember to make and test backups for the future. Even if they had customer support, if that customer support had a backdoor to unlock your account it would be regularly used by malicious parties to steal people's accounts & data.