** U.S.-listed shares of Russian mobile phone operator up 4.2 pct at $7.22
** Citigroup raises to "buy" from "neutral"
** Of 18 brokerages covering the stock, 6 have a "buy" or higher while 12 have a "hold"
** Oil prices are expected to rise in 2016, and economic sanctions against Russia may be revoked by June 2015, which may benefit the company, Citigroup analysts write
** Stock had fallen by about half since company reported Q3 results on Nov.25