My car broke down, blew a head gasket. It was an old car. I decided to find someone who would take it for cash for clunker sort of deal. I contacted a car shop who offered $600 and free tow service. I accepted (via texting and calls). The shop was a coworker's relative so i trusted them. They later reduced their bid to $300, so i said that i wouldn't accept anything less than $450. They said that i could go somewhere else with my car, but they would charge me the towing charge. Do i have any leverage here? Are they allowed to charge me for the towing fee?