How to solve the problem with two SIM cards?

Question

Mobile devices

Good morning.
There is xiaomi readmi 3 pro se.
There was a problem with using two SIM cards. The first is from Kyivstar, the second is from Vodafone (Ukraine).
The Kyivstar card works without problems, but the Vodafone card can only receive incoming calls, outgoing calls do not occur.
I checked a phone with two SIM cards from Kyivstar - everything works, you can receive a call and make a call without problems from two cards.
Put "vodofon" - only incoming.
How to solve the problem?

Answer 1

Strange things are happening. They put two "vodofone" cards - it worked, which caused such a glitch is not clear. Now they have returned to Kyivstar + Vodofone and everything works.
The issue was resolved.

Answer 2

the easiest way is on w3bsit3-dns.com
but in general look at frequencies and internal roaming