Booking.com Charged My Card £180 for a Flight I Never Booked

Today I discovered a pending transaction of £180 on my bank account with the description “bkg booking.com flight London”. I have not booked any flight with Booking.com or Booking.com Flights, and I have no knowledge of this reservation. I have used Booking.com only for hotel bookings in the past and have never booked flights through them. My bank advised me to contact Booking.com about this payment, but I am finding it extremely difficult to reach their customer service and have not been able to speak to anyone so far. I request that this unauthorised £180 transaction be urgently investigated, any related booking be cancelled, and that no money be taken from my account for a service I did not book. I also ask for written confirmation that my details are secure and that my payment information will not be used again without my consent.