Failure to cover my claim

I was involved in an accident, i hitted the *** on my way from home (venda) to polokwane (my workplace), i reported and submitted everything to my insuarance but i was told to pay R25000 instead of an agreed R3500 EXCESS amount, so they are insisting on refusing to fix my car before i pay R25000, it is so unfair, and my car is still not yet assessed...I need help. thank you!