Hello,
I have a very good customer in Hungary, whose Mastercard gets declined intermittently for unknown reasons. We sell very limited quantity collectibles, so when his card declines, he misses out on his purchases.
He has contacted his credit card company multiple times, but they say there is no problem on their end.
Over the past few months he has become so irate, we are about to lose him as a customer. How can we ensure that his transactions will complete?