Samsung A34 5G wifi calling

It is a pity that Smarty don't implement the calling preference option between WiFi and the mobile network like other providers do. 

You are correct, the prefer wifi calling option I had with the EE sim has gone with  Smarty. Although I do get a better cellular service now so it shouldn't be an issue.

The other issue I had when my number was ported was the phone number tied with the sim remained with the original number, but as others have done, I fitted the sim into an old iPhone 6 and went to conacts, and that has updated it.

GrahamS_1507134 Not sure why mobile data will affect calls or texts.

No, no need for mobile data to be on for WiFi calling to work.

There is an easy solution to make sure you have wifi calling working when you want it, such as at home. Just put your phone into airplane mode and then turn WiFi back on again. As there is no mobile data connection, WiFi calling is the default, and only connection method. If you have mobile data and WiFi calling on and there is the slightest of mobile data signal, then  the phone will not use WiFi calling. You have to make sure that there is absolutely no mobile signal for WiFi calling to be activate. Don't forget to get out of airplane mode when you go outside though.  

If there is any mobile signal available, even if you have WiFi calling on, you will not get WiFi calling (unless you are using an iPhone as they seem to work differently). To guarantee WiFi calling when at home, you have to turn airplane mode on and then turn WiFi on again which leaves mobile data off. Then you will get WiFi calling.