No VoLTE or Visual Voicemail on Android

[Gee333]

Hello.

Please could somebody advise.  I joined O2 last week on a monthly SIM only contract.  I have ported my number over from previous provider. I have phoned the call center numerous times and have got no where. I cannot activate voLTE or visual voicemail on my Galaxy S20. It was working on my previous provider.  Any ideas? 

Thanks

[Enlli]

You won't get an icon in the status bar with O2. You know it's on if the phone stays on 4G when making a call.

[Gee333]

@Enlli thanks for the reply and update.