As the website link also states the same email address that you have already tried, maybe @Martin-O2 can check which email is actually valid currently?
We had problems with the change of name form last year. It was withdrawn for a while until O2 corrected it and then it worked.
It looks as if there are problems yet again, so we will need to see what @Martin-O2 (one of the community managers) has to say.
@Martin-O2 also needs to check the link given by @Bambino as part of that doesn't work either. The line I've highlighted doesn't actually take you to any form..just refers you to the contact us section
Veritas Numquam Perit
I can certainly get someone to look into this for you @Harlequins. I'll need a few details so will drop you a private message so we can talk further.
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