I think it's rediculous how these people can bill us for a mis-calculation that was there fault in 2009 and decide now it's time for us to pay them back.
I think they need to take the hit and it's lost revenue, I work in retail myself and if I make a mistake and under charge a customer on their bill I can't just call them to come back and pay the difference that I messed up on. This is something they need to just suck up and get over.
Then they want you to call and wait on hold for hours at a time to set up payment arrangements only in four to six month incriments to pay off something they they should be taking the hit for.