Cannot access or reset authentication method of my Self Assessment Account

I am writing to seek assistance with an issue I am experiencing with my Self Assessment account. Currently, I am unable to access or reset the authentication method for my account. The problem began because I no longer have access to the authenticator app that was initially used to set up my account. I have called support multiple times for assistance, but unfortunately, they were unable to verify my identity. As a result, I am now stuck and unable to manage my Self Assessment tax account directly. This situation has forced me to rely on third parties to pay my Self Assessment tax, which is not ideal and causes significant inconvenience. Could you please advise me on the steps I need to take to regain access to my account or reset the authentication method? Your prompt assistance in resolving this matter would be greatly appreciated. Thank you for your help.

Hi,
For assistance you will need to contact our Online Helpdesk:
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Thankyou.