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We are going to St. Petersburg for a week and we would like to buy a sim card for our Samsung smartphone, so that we can use phone and Waze. I looked for russian sim-cards in Google and all I found were plans with daily or monthly payments, that probably require a credit-card. Is there a way to buy a pre-paid sim card without a credit card? If so, what is the best place to buy - in the airport or on street shops?