Tele2 Russia is running a promotion with Xiaomi, offering discounts on Xiaomi smartphones in exchange for unused voice bundles, including bundles purchased on the platform Market Tele2 or transferred from other operators when porting. The promotion is valid in both offline and online Tele2 Russia shops. An exchange rate of 1 minute of calls for RUB 1 applies.

Source: https://www.telecompaper.com/news/tele2-russia-offers-swap-of-voice-bundles-to-discounts-for-xiaomi-smartphones–1403857