1. It's a proper noun: the name of a place; i.e., the Customer Service counter; 2. 'car' is not a proper noun; 3. Customer Service (proper noun); The Customer Service counter (proper noun functioning as an adjective. 'the' modifies the noun 'counter'; 4. is incorrect. "a" can't modify a proper noun, and there isn't a noun in the sentence for "a" to modify.