LG U+ Korea and Iphone SE from Russia

Hello. I have a problems with an Iphone SE from Russia in Republic of Korea, Cell Operator LG U+.

Cellular signal is absent, but LTE indicator is on, Internet works fine. Cellular voice calls, SMS dont works.

Help me please.

A few days ago This phone worked fine with this uSim card. But i removed usim and inserted in korean LG U+ phone. After re-inserting usim in Iphone - i got this problems.