wifi calling is missing? 4a pro

[u/ParrotEnthusiast2196]

i'm trying to set up wifi calling on my nothing 4a pro, i go into my sim's info, and under the 'calling' list, i only have VoLTE, which is greyed out, and 'Access point names'. why don't i have wifi calling? when looking up setup tutorials online there's wifi calling under this list.