Just do it, okay?!

It's bad enough that I have to work with someone who walks around like he's "too cool for school," but why does he have to fight me on something miniscule that I ask him to do for a huge project I've been working on for the past 4 months? In the time that we've gone back and forth about whether this teensy but hugely important change should be made, he could have made the change a dozen times already! I know you're busy, but I'm the customer here. Don't argue with me; just do what I ask and we can both get on with our lives. Please and thank you.