Access Denied To My Booking.com Account

I have been unable to access my Booking.com account for around three years, ever since I moved from Belgium to the UK and changed my phone number. When I try to log in with my email address, the system always asks for verification via the old Belgian phone number that is no longer in use, so I am completely locked out. Because I cannot get past this verification step, I am also unable to contact customer service through the usual logged-in channels and I have found no way to update my phone number or verify my identity by another method. I request that my access to the account be restored and that my phone number be updated from my old Belgian number to my current UK number, or that another secure verification method be offered so I can use my account again.