“mazda dealer”
Say no more. If the car isn’t under warranty or in for recall service you don’t have to use a dealer. A Mazda is just a car and any good independent mechanic can deal with it.
I am especially skeptical of any place that would even imply that you could replace only one strut. That is really poor practice - just plain nuts.
Lots of shops will do a basic suspension system check as a courtesy. Get a second look from someone else.