Can you comment on the 5 day warning, though?
Speaking as a quality professional with some experience with billing, the idea of identifying and transitioning to a new payment processor with proper testing and zero business downtime within 5 days isn't very realistic. If a company abstracted their payments up front, great, but for a small firm it's likely there's tight coupling there. Customer communication also isn't instant, and I assume subscription authorizations have to be transitioned as well--probably by the customers themselves.
It would be one thing if you stopped people at the door, but once they're dependent this seems rather harsh unless they've somehow egregiously violated business ethics in a way that's harmed you. You're pretty much guaranteeing a business interruption, and that can be fatal for a small firm.
And from a strictly pragmatic point of view, this is the sort of action that would make me hesitant to pick you for an upcoming project. When I judge risk vs. worst case outcome, the very fact that your worst case is a surprise interruption would put you on the wrong side of the line even at a low risk.
This is essentially a provider uptime decision, and it's easy to see this as unpredictable between 5-9s and zero. That's not a good quality for a payment processor.