Apple Music via EE promotion not working

Is anyone else having this issue? I have a contract with EE for my iPhone 16 and as an added "inclusive extra" they gave me the option to get Apple Music for free however whenever I try redeem it through the promotional link they send, it goes onto Apple Music and just says "This subscription is already being used with a different Apple Account". I've gone ahead and contacted EE but they said that the promotion isn't even linked to an Apple account at all and therefore must be an issue on Apple's side, I called Apple and they went through everything they could but claimed it was EE's fault with their link and suggested I call them back. I have been on call with customer service between Apple and EE for the past 3 days and this is honestly ridiculous that no one can get it fixed.

EE has even gone ahead and tried switching the "inclusive extra" from Apple Music to Apple TV+ and that managed to work but then when they reverted it back to Apple Music, the promotion for Apple Music still wasn't working

I don't have any other Apple ID, I don't have any existing Apple Music subscriptions, I have reset my network settings, I've tried making a new Apple account, I've even gone in store to one of EE's branches to see if they could do something and nothing has worked. I'm stuck on what to do could someone please, please help because this is so frustrating!

[Edited by Moderator]