Booking.com Pending £477 Charge for Cancelled Blackpool Booking

I am writing about an issue with a hotel reservation I originally made in Blackpool through Booking.com, which I then cancelled when I decided instead to stay in Liverpool from 2 to 4 October at The Shankly hotel. After cancelling the Blackpool reservation and booking The Shankly in Liverpool for 2–4 October for approximately £482, there is now no trace of the Blackpool booking in my Booking.com account or app. However, today a pending payment of around £477 related to the Blackpool stay appeared, even though I had cancelled that trip and there is no active Blackpool reservation showing anywhere in my account. For the last two hours I have been trying to contact Booking.com customer service in the UK without success, and this situation is causing me a lot of stress as it is a large amount of money just before my trip. I request that Booking.com urgently review this situation, recognise that the Blackpool booking was cancelled, stop or remove the pending £477 charge, and ensure that I am only charged for my confirmed Liverpool stay at The Shankly hotel from 2 to 4 October.