This is usually a low charge but it could be a bad blend door actuator as well. Hands on inspection is needed.Here is a link to find a shop near you. A 2nd opinion is always a good idea.
https://repairpal.com/repair-shops
Alex
RepairPal Certified shops can diagnose and repair your 2009 Mazda CX-9. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.