Then u cant use this method. Try this:
https://forum.xda-developers.com/poco-f1/how-to/guide-activate-vowifi-wlan-call-t3871263
https://telegra.ph/Trying-out-different-PDC-profiles-on-devices-with-Qualcomm-SoCmodem-to-make-VoLTEViLTEVoWIFI-work-07-03