So, I'm with you on the GroupOn Fucker that ruined this. I hope Sean and the gang got handsomely rewarded for their years of work.
I'm stuck with a merchant account provider I detest, that's raised my rates just about every month for 3 years, because there's no way to get my customers' info back out of the payment gateway. It's either keep wasting money on rates nowhere near what I initially agreed to, with lousy support, or lose even more money by asking every customer to re-enter their billing info. Just a few percent deciding to ignore the mail and let their subscriptions lapse would be more costly than the fees.
These days, in the US at least, there's affordable options for both payment info vaults that can connect to multiple gateways, or gateways offered by merchant companies that will give you your data if you decide to leave them. A few years ago, that wasn't really the case.
Since users have to update their info when their cards expire, can you start vaulting cards in two places, and slowly migrate away?
To those who don't respond the first time, give them an offer for an X% discount for loyalty or something of the such. When they try to take advantage of it, then ask them to give you billing information once again.
You should hit 99.9% with that, and either take a loss on the custoemrs left over or more likely keep the legacy customers alive for years on to come.