VoLTE is not working on sim 1 slot. please fix this bug. You didn't fixed it beta 5 Update .i already reported in beta 2 Update. because of VoLTE is not working on sim 1 slot . i can't make calls and receive call. 1)look in 1st screenshot top bar their is no VoLTE working. while using sim in sim 1 slot. 2)In 2nd screenshot top bar their VoLTE is working, when Same sim used in Sim 2 slot VoLTE is working. I am using Jio Sim which is 4G LTE and VoLTE too. There is no problem with sim card. Its bug or error of software it should be fixed in BETA 5 update but it didn't. Before this UI 2.0 their was no problem of VoLTE on sim 1 slot.
Try and checn whether Access Point Names is there or not becuase i faced the same issue but i mannually configure the Access Point Names and its working fine for me. If you don't know how to configure peobably contact your network support team and request them to send you the configuration for APN. once received goto APN and select the option available. it will start working fine then