Eyewitnesses said the car was travelling at a speed of around 30 km an hour. Police are looking for a white van and asking eyewitnesses to come forward.
The Romanian woman suffered severe facial swelling, multiple abrasions and possible concussion. She was taken to hospital and given first aid.
She said the man had picked her up on Vogelweiderstrasse and taken her to his home in Lehen, police spokesman Anton Schenz told the Austrian Press Agency.
After the woman had provided her services he had offered to drive her back but en route he snatched her purse, opened the passenger door and kicked her out of the van.
"He must have kicked her out with some force - she was still holding the door handle in her hand,” Schenz said. She rolled over several times in the road, and eyewitnesses called an ambulance.
The woman described the man as slim, around 1.8 metres tall and with dark hair. He was driving a white van which had no windows in the back.
Police are asking witnesses who saw anything at around 11:10pm in the Bessarabierstrasse to report to their nearest police station.