It would be the person who made the request who says "never mind." So you're right -- "never mind" is an odd thing for the second person to say. It's a poor question. You could argue that "No problem" works because he's saying "No problem remains" or "There's no longer any problem."
I didn't assume there actually were 2 speakers in the original. I think 2 people were present but I think both lines were spoken by the same person, perhaps with a break in between while the second (silent) person went to turn off the radio and get the ladder.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.