I have recently been in St. Petersburg. I needed only to be in the city, so I had no problems with "roaming" in whole Russia.
In any case, at the arrivals exit hall of St. Petersburg airport there are 2 shops. One of them is Beeline. It proved to be the one offering the cheapest offers (I checked both).
250 Rbs for 5 Gb 4G data, imprecise and big (for my purposes synonym of unlimited) voice time to Russian numbers. Valid for whole Russia (so they told me). All lasting for 7 days.
5 minutes procedures. I was on-line immediately. People at the shop very efficient. They seemed to know (and most likely did knew) what I needed and did not want to be asked too many questions.
Occupied to sell SIMs "by the dozen" to informed travellers.
Worked as a charm. No hassles, no doubts, no problems, no bad surprises. Out of the airport with all services on in 10 minutes. It has never happened to me in any other part of the world.
DL in the whereabouts of 30 Mbit/s.
Sleepy