yes. most of volte enabled devices supports wifi calling feature. but it depends on sim operator u r using. if ur sim operator supports ur devices for wifi calling then u can enable this feature in ur smartphone from setting menu. otherwise wifi calling option will remain disable. at present jio sim supporting most of volte enabled devices for wifi calling but in case of airtel it is limted right now.
In coming days airtel will also supports most of the volte enable devices for wifi calling. at present for j7 max u can use jio sim for wifi calling service.