Login issue with Self-Assessment account and lack of support from HMRC

I am experiencing issues logging into my self-assessment account due to losing access to my phone number. I know the login and password, but unfortunately, the activation code is sent to the old number. I've tried to log in three times through the recovery account, and despite having all the documents in front of me (P60, payslip, driving licence) and entering the information, HMRC couldn't confirm my identity. I've tried twice through online chat, with the same result. I pass the first data verification, but unfortunately, I don't provide correct information according to them in the second. I also tried calling, after 45 minutes of being on the phone and an attempt to transfer me to another department, the call was disconnected. Other attempts ended up in the queue or with an automated service that wouldn't redirect me to any advisor. Does anybody have idea what may I do in this situation? Thank you

Hi kasperkacpersky,
If you are unable to self serve to reset your telephone number then you would need to contact our online heldesk for further assistance.
You can contact HMRC here:
Technical support with HMRC online services
Thank you.