Towtruck company *****s my car

My car was towed by Speed spares and services on the 28th of July at 19:30 at a agreed price of R750.At the time they hooked the car I told the driver that I only have R450 on me but I will make a plan once we get home.Due to the hour I could not find a R300 and without any discussion the driver took off with my car.The next morning the 29th of July this people wants R4990,00 from me to release my car.They claim my car became a salvage a word I do not understand as the car was not saved from anything.Still today I haven't seen my car Orr hear from them How can anything inflate from R750 to R4990,00 overnight I did not agree nor signed anything till this day This is ******ion