When I use data on first sim second sim get no service.
Have you enabled dual sim 4g? If no then enable it from settings > network > sim card
I did enable dual 4g Thanks
Check your both sim support volte . Also, check of by any chance you got a version of rog phone 2 which does not support volte .
You can see volte in one sim it's a volte phone and both sims are volte
We need to log your phone to see what's going on. If you're OK with that, please reply to this comment and I'll send you a PM with instructions.