Please do pardon my rant, but how on earth can it be so difficult for me to change my mobile number on my Privilege Club account?

My old work number is associated with my account and I have recently changed jobs meaning that I cannot receive the OTP code to log in.

I have called several times to try and update my number and been advised to email “[email protected]” to make this change.
I have done this several times since Christmas and still no progress made - every time I call, they are utterly useless.

Is anyone able to advise on any other avenues I could try to make this very simple change to
my account?