Enterprise Rent A Car Enterprise Unauthorized Charge to Credit Card SAINT LOUIS Missouri

My Car met with an accident with another car, It was at fault of other driver and he agreed the same. The insurance company of other driver agreed to pay all expenses my car repaird and a rental car for the period when my car is at Body Shop. so the Insurance company has booked a rental car from enterprise for me. The rental car agent called me to verify my identity and pick up date. during the conversation he offered an upgrade if i am ready to pay extra amount apart what Insurance pay. I rejected the offer and clearely told him to give a car for the Limit Insurnace pay. 

On the day when i dropped my car at Body Shop, Enterprise Agent brought rental car to the Body Shop location directly. By Looking at the car they are giving to me, I surprised because it's full size 8 Seat Van.

First i rejected that car because i dont want big car to drive everyday to work and moreover i need to pay extra for Gas as it consumes more gas compare to Economy car. She told no other cars are avialable.

Once again i asked the agent if I need to pay anything extra or will it be covered by Insurance. She told me, everything covered by Insurnace company, i dont need to pay anything extra for rental period. After completing formalities, she tool my credit card detials for security deposit. Everything seems good, i drove away happily to my work.

After one week, when my car was ready after repairs, I dropped the rental car at Body Shop as they have a tie up with enterprise and drove away with my car.

Later next day, Enterprise agent called me told that everything OK and they asked me to pay extra amount as i took a Big Car. First thing My Blood got boiled to 200 degrees and then i controlled myself and took deep breath. Then i replied softly  whatever the conversation I had twice with them before. Then he replied, they will check with insurnace and they dont charge to me. I thought it was a confusion from there end. 

Once again i got shocked after 15 days, when i see my credit card bill with a charge of $150 from Enterprise rental car, immediately i called them. a lady answered to me and after long conversation she told it's mistake from there end and they will credit back the amount to my credit card. But they never credit back amount to me also when i dispute the transacation through my Bank ...Enterprise rejected the dispute.

Now i am looking for help to deal with this situation.

First thing I decided not to rent a car with Enterprise in my life and warn everyone in my circle not to go enterprise.