This keeps happening to me - 3 times in the last week. If I change my password I receive a 2FA code. If someone else unauthorised changes my password, I don't receive anything. Given this is happening to a number of people, I think there is something wrong with BT's security. Their help desk is useless in trying to solve this.
I have moved you onto your own thread so that you get answers regarding your problem and not confused with OP of the other thread you posted on.
Do you have any "Password Manager" programs on your device?
How many devices do you use to access your email account?
Do you use an email client or a web browser to access your email?
Do you use a VPN?
Do you use anything such as "Mail Washer" on your device(s)?
Yeap, exactly the same thing happening to me, you would think with all the money they rinse of us, that they could hire someone decent to find the problem, or at least admit they have an issue and offer to turn off password change without additional auth!