whenever I try to call my mum's UK landline number from Belgium keep getting voice message saying the number is not in use.
I can call the number from my Belgian phone/SIM and I think I can call the number successfully using the Virgin phone whilst I'm in the UK.
Thanks for getting back to us @FroogHandler.
Sorry that you're still unable to make calls to a specific UK number whilst you're roaming. I would like to take a closer look on your behalf. I am going to send you a private message. Please look out for the purple envelope in the top right of your screen.