First help negligence in handling business

On the 3rd of August was involved in an accident in Pretoria north the first help person offered to tow my car initially said was for free then later on changed and said was charging for the towing after the car was towed i was also coheced to sign the tow slip without reading the t's and c's now the person says because i signed the slip then i concerned to the amount however even on the tow slip there is no tow amount that i apparently concent to now they are refusing to release the vehicle without payment which i did not agree to