To use SIM card video call, you should check the requirements below:
1) Video call requires network/SIM card support, please contact your SIM operator to make sure you have the video call service.
2) Please go to “Settings”->”Network & internet”->”Mobile network”, touch trigger to active “VoLTE”
3) Go to “Phone” app->touch menu key at the top right corner on the screen->touch “Settings”->”Calls”->touch trigger to active “Turn on video calling”.
4) Make sure called party also support video call and his/her SIM operator is the same as yours
Video call option will appear during voice call is connecting when above requirements are met.