Unable to use 4G for calls (incoming or outgoing) when at home

Hi,

I have for the a number of months now not been able to make or receive calls when on 4g at home. To be clear, there is no issue with my phone picking up a 4g signal at home as I have 3 out of 4 bars on my signal strength and I can use 4g for using the internet and accessing apps etc. My phone previously worked on 4g at home too.

When I first encountered the problem I spoke to customer services who said it was a SIM issue and they would send a new one, which they failed to do.

I have spoken to the Know How team at a Carphone Warehouse store and they said it would not be a sim problem anyway.

I do not have not encountered problems using 4g for calls elsewhere.

Receiving calls, or more to the point, not being able to, is more of an issue than making calls at home as I can use a landline but if someone tries to call me I am unaware they are calling, I do not get a missed call message and if I then try to retrieve a voice message I am unable to call my voicemail either.....

It is very frustrating and as I am SIM only I am seriously thinking of going to another service provider.

Thanks for your time.