WiFi in Kiev (Kyiv) and Calling Ukraine
International dialling instructions for calling Ukraine, including internal calls and WiFi in Kiev

Bring a spare phone with you to Kiev (Kyiv). Sim cards are really cheap and you can save yourself a lot of data usage (and money) by using a local SIM card. There are lots of places to purchase them from but be careful to check the tariffs.
WiFi Connectivity in Ukraine
Kiev (Kyiv) is a modern city with high technological skills. You will not necessarily need a local SIM card as you will have no problem finding WiFi connectivity, almost every restaurant, hotel, bar and cafe supports this.
Although you will not need a local SIM card, it might be a good idea to purchase one anyway. They are extremely cheap, easily available and will save you racking-up expensive call charges on your home phone.
If you are in the centre of Kiev you will easily be able to purchase local SIM cards from just about anywhere. The moment you set foot on a main street you will see many little kiosks.They sell everything you’d expect; drinks, magazines, cigarettes, snacks, and of course SIM cards. But for the best advice go into a dedicated store.