Mobile Phones
Mobiles are more popular with the local Muscovite than Japanese cuisine, drinking cocktails, shopping and fashion tv all put together. You can use your mobile phone from home if your provider has a roaming agreement with a Russian mobile company. It'll cost you though. If you call with your mobile to a Russian number, you'll need to put in all the numbers starting +7.
Russian SIM cardsIf you want to avoid exorbitant roaming charges, just stick to texting or get a Russian SIM card. They range in price starting from 200Rbl up to 400Rbl depending on your chosen package. You will be asked to show your passport when you sign up for the SIM card - this is so that if you lose your phone, they can than provide you with a new SIM card that uses the same phone number.
The main providers in Moscow that provide the most reliable service are:
Megafon
Beeline
MTC
You can top-up your Russian pay-as-you-go SIM card at any of the top-up machines that you will find in most underpasses and phone shops. Just choose the provider you need on the machine's touch screen, type in your phone number (without the +7) and then insert the amount of money you want to top-up by.