Weird. That's the exact opposite of my experience. I've had a number of odd rejections that led me to reach out to a couple vendors (hey Amazon, I'm looking at you!) because there were small transactions attempted against closed cards. I've had a few hiccups for things like creating multiple cards to use with PayPal (there's an avenue for fraud there, apparently) but I've been able to get those resolved quickly every time. I have nothing but good things to say about their offering and it's nice to see they're opening a read API (I'm hesitant about write keys).
My only complaint right now is that some vendors (Google specifically) reject their card numbers because they're pre-paid and they've made a decision in the last year or so to stop accepting them. I know for a fact this is a new thing because I'm paying for a Fi account and a Google Music account using privacy numbers. When they finally expire, I'll stop giving Google money altogether.
I'm really sorry to hear about the negative experience. This is surprising to me, and I’d be happy to look into the specific case - can you drop me a note at [email protected]?
I would not recommend them. Their marketing is dishonest, claiming that transactions cannot go through if the card is closed, while in truth merchants are able to "force post" debit transactions even when closed.