I Can't Reach Booking.com Customer Service For Date Change

I recently made a hotel reservation at the Palm Hotel in Waikiki through Booking.com. Since completing this booking yesterday, I have urgently needed to cancel the reservation and receive a full refund, but I have not been able to reach your customer service despite multiple attempts. The local phone number listed on your site does not work, and I was never able to reach anyone. This situation is extremely frustrating because I have an urgent issue with this reservation, yet there is no accessible or functioning support channel to help me resolve it. I request that my reservation at the Palm Hotel in Waikiki be cancelled and that I receive a full refund as soon as possible. I also ask that you review and update the contact numbers shown on your website, so that they are accurate and working, and customers can actually reach you when needed. I expect someone from Booking.com to contact me directly as soon as possible to confirm the cancellation and my full refund, or to provide a working customer support phone number where I can promptly get assistance. I expect this matter to be taken seriously and resolved swiftly.