I have not received payment -but billed for commission

For the last few bookings in the early part  of this year, i did not get payment and only an invoice for payment. Few tele collections persons called and i explained them. They said they will get back.

My bookings are suspended. But I am doing good business on Airbnb,

How may I contact someone in booking.com on phone to explain the deadlock.

Thanks in advance

Oscar ./ Upendra