Two classic taxi problems in Saint Petersburg: the driver asks for twice what the app quoted, and the "cheap ride" offered to you in the Pulkovo arrivals hall. Both are resolved in your favour once you know two things — the price shown in the app is a contract term, and the aggregator is liable for a car that is not in the official register.
The app price is the price
The fare the booking service showed before the trip is an agreed price, not an estimate. You do not have to pay more, unless you changed the route yourself — added a stop, asked the driver to wait, or requested a detour. Pay in the app rather than in cash: that records the amount, the route and the time, which is exactly what you need if you later claim the money back.
You are entitled to a receipt
A cashier's receipt must be issued at payment — electronically in the app, or on paper if you pay cash. No receipt means no proof that you paid this particular car.
Who is liable
Under Russian federal law 580-FZ, the taxi booking service is fully liable to the passenger for harm to life, health and property if the passenger was not properly informed who the carrier is, or if the vehicle is missing from the register of taxis and the carrier's right to use it is missing from the register of carriers. In other words, "we are only a platform, a private driver took you" does not hold.



