Them - "It isn't working. What I'm I doing wrong?"
Me - "What are you doing now that isn't working?"
Them - "I'm trying to use the software. Why aren't you helping?"
Me - "Because I don't know what the problem is."
In another case:
Them - "I'm giving you one more chance to help me with this, or I'm giving up."
Me - "This is the first email I've received from you on this."
Them - "I don't care... I sent one yesterday, and you didn't reply."