Siri sometimes misinterprets what I say but I may be saying things that are too complex or related to notes about contacting people. Maybe I just have really bad speech pronunciation. I do mumble sometimes I must admit lol
My problem with Siri is names. It will try to correct names to non nouns. This is a huge issue for me because I want to use it for directions. Coincidentally roads have names so it tried to change them.
I find that Google works 10x better! I suggest using their search.