Everytime I have had to dispute something (which off the top of my head I think is 4 times in the past few years, 2 for fradulent charges) I simply explained to my CC company what was going on and why I wanted to dispute the charge and they took care of it.
If a mistake was made during purchase and customer sevice is unresponsive to fix it then that would be a legitimate reason to dispute in my opinion. The credit card company just wants to know you made a good faith effort to solve the problem before getting them involved.