Unable to reset Apple ID password

I got anew iPhone for my son in January. He had to set it up manually as the camera on his old iPhone had broken. We were unable to reset and had to wait 3 weeks for an email to restore his or something, I forget as this has been going on so long. Anyhow, we get the email and he goes to reset password, a call comes through with a verification number which we then input and has to wait again for 24 hours for a further text which then never arrives. We try again and we go round in a circle again.

so my question is, how can we get this sorted? He has a fab new phone he can’t fully use. I tried Apple support chat but again we didn’t get a text and have now not tried again as support said the more you try, the more it looks dodgy so we’ve left it around 3 weeks.

Can you cancel your Apple ID so a new one can be created? He has kept his original mobile number so can it be disassociated? Would that sort it?

Whilst I understand security measures are in place to protect, I am looking at a formal complaint as this is becoming ridiculous.

Sorry for the essay, hoping someone can help