It sounds like your insurance company is determining that the scrape and tear to your convertible top caused by the opening of garage door to be collision damage, which does make sense. Collision coverage is basically defined as covering damage when a car, other vehicle or object hits your car. The garage door could count as an object striking your vehicle.

Comprehensive coverage is usually defined by covering damages caused by flood, fire, theft or being struck by an animal. You can contact the Massachusetts Division of Insurance to make sure your state's definition for comprehensive and collision match up with the basic definition you have received here. You also can speak to your insurance agent to get specifics regarding your policy.