Thanks. We had already done that... and the support person said the only thing we could do was refund the clients and ask them to pay us again with new invoices with a different payment method. 

THIS IS A TERRRRIIIBBBLLLEEEE customer experience recommendation. We said no of course. Many times. And insisted that QB work on it. The agent said that he takes this exact call all day and that was the only option. He repeated that multiple times.

Then when we screenshotted the support thread here showing that an account credit was possible, the next agent was suddenly able to help. 

I hate that you have to practically yell at a random bureaucrat in the morass of support systems for large companies to get them to do the right thing. 

So if anyone is reading this -- no matter what the support agent tells you to the contrary... they do have the power to credit you fees that shouldn't have been charged. You just have to insist.