Booking.com - Pathetic

I have been struggling to get a refund from booking.com since apr - they advised they did the refund 15 May and it takes up to 30 days, however still nothing - my bank can not trace it on the ref no they gave - I HAVE BEEN ASKING THEM TO SUPPLY ME WITH THE ACTUAL PROOF OF PMT OR THE BANK DETAILS THEY USED TO DO THE REFUND - BUT TO NO AVAIL - THEY KEEP GIVING ME THEIR REF NO AND I KEEP ADVISING MY BANK ARE UNABLE TO TRACE IT ON THEIR REF NO...........THIS HAS NOW BEEN GOING ON SINCE 15 JUNE AS I WAITED OUT MY 30DAYS.....
BOOKING.COM IS NOT TRUSTWORTHY PEOPLE AND PEOPLE SHOULD NOT BOOK THROUGH THEM.....