Can’t ring in or out on my phone

Hi MarcusBur_62344 👋
Are you in the Midlands? If so it's because the 3G network has now been turned off and your phone is not supported by SMARTY on the VoLTE network.
First off, you can use this link to check if your device is VoLTE compatible
https://help.smarty.co.uk/en/articles/8985136-checking-if-your-device-is-4g-volte-compatible
Even though your phone may be provisioned for VoLTE, SMARTY doesn't support every make/model and if it's not on the list in the below link then it won't work. You will still be able to send/receive texts and use your data but not make/receive calls.
https://help.smarty.co.uk/en/articles/4237414-which-devices-are-compatible-with-wifi-calling
There are only 2 options:-
1) Purchase a SMARTY compatible phone so that it works on their network
2) Change to another provider. You should be able to find the approved devices on their websites that are supported for use with their VoLTE network.
You are correct in saying that the web chat is useless as I had the same problem. I was advised to order a replacement SIM.... that wasn't the problem, told to contact the manufacturer to get the VoLTE enabled ..... VoLTE is enabled but just didn't connect, to try using my phone for a call when away from home.... tried it ~5 mies away and nada, so MANY suggestions were made by them and nothing worked.
What SMARTY won't admit to is that it's because they don't support your handset and will make you feel like the problem is down to you/your phone! I also spent >3hrs (twice) on web chat and got no where!
I finally made the decision to change to iD Mobile, they have comparable plans to SMARTY, as my phone was on their VoLTE Approved List i.e. tested for use on their network, and the range of approved phones for use on their network is far larger than SMARTY.
I hope this helps! (If you are not in the Midlands then I apologise as I don't know the answer.)