What should I do when a taxi driver asks for a fare higher than what is customary or what the meter determines, knowing that the state requires the installation of a meter, but drivers do not operate it?

The taxi owner and the passenger must adhere to the rules of ijarah (leasing/hiring), which include knowing the fare before commencing the service. If a known fare has not been agreed upon, then the ajrat al-mithl (customary/market fare) must be paid, which is the commonly accepted fare for such a service. By paying the ajrat al-mithl, one's obligation is discharged.