Why iPhone is more expensive than in the USA but fully doesn't work? I overpay money for mythical LTE? I bought phone in the USA it supports the band 7 and 20 which theoretically work in Russia, but phone doesn't work. For what I paid? For the camera and the scanner of prints?
If you wanted LTE support where you live, then you should not have purchased your phone in the US. US iPhones are only guaranteed to support LTE in North America, no where else. If you wanted LTE, you should have purchased your phone in Russia.