Unable to receive/make calls when connected to vodafone wifi

[Leeleec78]

We're unable to make or receive calls when connected to wifi at home, we have to turn off wifi in order to make calls.
Both have iphone 17, vodafone broadband and Three ultimate phone contracts.
IOS 18, network Three 64.2. 
Calls via whatsapp or messenger work fine, it is just calls over the three network

Where we live has very poor 4G reception area so we are reliant on wifi calls mostly when we are at home. We both have disabled elderly parents who may need to get hold of us in an emergency but can't as they don't know how to use whatsapp or messenger. Besides this, paying for a phone contract so shouldn't have to be reliant on whatsapp to have phone calls.
I can see others have had this problem, is there a solution? Is the culprit the phone network or the broadband? If there isn't a solution, one will need to go.

[PeteG]

Hello there. 

What is happening when you try to make a call? What happens when someone tries to call you?

Pete.

[Leeleec78]

Calls going out don't connect so just dead noise our end, the person we call receives the call but with silence on their end.

Calls we receive don't connect and we get a notification of a missed call

[PeteG]

Since you're able to make calls with the Wifi off, it might point to an issue with Wifi calling. Normally I'd recommend having it on for situations where you can't make calls on the mobile network, but since yours is working when Wifi is off, it might be best to turn off Wifi calling. 

Pete.