When I dealt with complaint calls over charges I was alway sympathic to the customers needs, and always tried to help - even to the point of breaking company guidelines, and thus putting my own job on the line.
However, there seems to be a group of people out there that think they have a right to "demand" (not "ask for" but, demand) their charges back.
When you have someone shouting abuse down a phone to you for over 30min, because they ran up hundreds of pounds in charges by writing out cheques with no money in the bank (and thus committing fraud), blaiming you, you do tend to lose interest in them, and not go out of your way to help them. How many people reading this thread treat call centre staff they way they'd like to be treated themselves?
Regarding your point about DD's I agree, to a point. The company is at fault for claiming early. One company I worked for only claimed on the date, or after, NEVER before. But there are some companies out there that do like to call early - but this isn't the bank fault. A DD is an agreement between a company and the account holder, the bank has very little to do with it. When I have had trouble like this in the past I have always claimed the bank charge back from the company who caused the charge.
And my personal advice - never use DD's - always Standing Orders - you control them.