Bank stamped cash depisit slips require pop recording

This message is intended for the Chief Accountant, person in charge of finance for Sun International payment for reservations. Dear Sir/Madam Could you please explain to me why any of the staff members in sector payments@suninternational would reject a bank stamped cash deposit slip with a booking conf Ref no and state the reason for rejection is no pop recording on the deposit slip. The wording (pop) meaning proof of payment. This is so highly unprofessional. My understanding and experience over the years with sector payments @ Suninternational is As and when I had emailed you a bank stamped cash depisit slip with a confirmation Ref on it would be taken and verified against your bank statements. Please correct me if my understanding is incorrect.