The inertia switch is usually in the trunk behind the lining on the right or left side.
Consult an owners manual for further more accurate direction.
Use this link to find some shops near you that can help with your concern:
www.repairpal.com/repair-shops
RepairPal Certified shops can diagnose and repair your 2011 Ford Fusion. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.