Beware refund clause in carhire

Although helpful to begin with delivering the car, I drove a car that had lost its gear stick and had the engine light on the whole time. Negotiated a better rate as my car was taking longer to repair and on returning was denied the rate and now have not received my deposit back within the stipulated 5 to 7 working days and the company is not taking my calls or returning emails. I am still waiting for the owner to respond. Not pleasant to deal with.