Yes bro, I replaced my sim because I was getting only 3G/2G network not 4G (LTE).
Bro, make sure these things:
1. Set mobile network to LTE or LTE/3G/2G
2. Check "mobile network type". It should be LTE. You may find it here open settings --> About phone --> Status --> Sim card status --> Mobile network type.
3. VoLTE switch is turned on.
If VoLTE still doesn't work, then contact CC. I think it has to be enable from their end. I remember when I converted my number from prepaid to postpaid VoLTE stopped working. After complaining to CC VoLTE started working. Same happened now.