@falalala If/when wifi calling activated can be easily accessed via the Quick settings Menu or Call settings via the phone App. see details here https://www.samsung.com/uk/support/mobile-devices/how-to-activate-wifi-calling-on-a-galaxy-smartphon...
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .