Budget Insurance is not all they claim to be

My son had a accident in December near Margate-someone drove into his cars rear end,which makes the driver of the back vehicle responsible to pay the damages.My son did his part,we reported the accident,got a case nr,as well asthe other drivers details which we gave to our insurance company..In January my husband spoke to someone at Budget,and they told us everything was organised,we can take the car in for repairs.When my husband phoned the panelbeaters to hear if the bill was settled by our insurance company,they told us nothing has been paid.So my husband phoned Budget-and according to them we are suppose to pay for the excess-wich is R11060-but as far as I know the insurance company normally claims that from the person who caused the accident.We had to go to a financial institution to borrow the money so we can pay for the cars repairs,how does it work then and why do we have insurance if we pay for the damage and they only pay a small amount???We can just as well not have any insuarance,and why are they not being honest when they sell the insurance?Are the insurance companies not suppose to pay the damages and claim it back from the person who causes the accidents insurance?