The unvalid credit cards

Hi, i have a situation here, actually a few problem ..

Booking.com is canceling booking after booking , because of invalid credit cards. That seems not correct. 

One of the cancrlled guest contacted me telling me that booking.com is having him back and fowarda about his credit cards, and the guest is telling me his credit card doesn't  have any issues. 


I need to know why booking.com is asking thrm about a a credit cards and still doesn't pay me if the guest doesn't show up.  Also  they pay on property , when they check in. 


Pls I need this to be fix a.s.p . Because Im loosing lot of business here. Hope to hear from someone soon.


Mrs Omira Barret.