Guest booked room that reflects different rate

I had a booking whereby the guest booked a 2 bedroom unit but the price turns out to be the studio price. When I checked the calender on rates, there is no mistake. I need Booking.com to check and revert what went wrong. This has happened a few times. I had no choice but to offer the guest 2 bedroooms for the price of a studio. During peak season (in Dec), I had a hard time explaining the error occurred.