And in both cases referred you to the Data Protection Team to request mailbox deletion.This is your right under the GDPR. But you do have to contact the DP team initially via any of the TalkTalk Contact Us methods and follow their guidance. If the DP team are ok with verifying you via email they'll certainly let you know.
You said you were not happy to send the DP team copies of personal data to verify yourself as the registered user and because of that OCE_Ady has suggested that you follow the Complaints procedures to involve a CEO office nominated agent try and resolve this for you.
The reason that deletion is not yet under your direct control is because the mailbox is still on a legacy mail platform rather than on the TalkTalk Mail platform with customers managing the mailbox deletion via their MyAccount that all broadband and Mail Plus customers use.
The next best thing that we can pursue is to authorise a password change with an ultra-strong password to secure the email account. This neither disables the mailbox nor deletes it but will make it as secure as possible.
Let us know your preferred choice.
I've alerted the TalkTalk Support Team and the next step is that they'll reply to you here and will then Community Personal Message you to ask for personal data to verify you as the onetel mail user.
NB The TalkTalk Team have OCE_ prefixing their username and Community Team as their tag so only respond to a data request from one of the Community Team.
Personal Messaging is via the envelope icon top right by your Avatar image on Community forum pages when signed in to Community.
Hi mikeonetel, I've sent you a personal message to obtain the information we need to reset the password for you.