system
A chat on subreddit /r/NoStupidQuestions
human
For sure, I totally understand this is an honest mistake and want to give them every opportunity to let them fix it.
gpt
If they wanted to use old shingles, they are not to be trusted to make it right. They are trying to trick you into doing a improper repair or incompetent. 

Contractors are not afraid to lie out the ass as long as there is no paper trail, and often even if there is.

I would find another company.