Roaming rates - Select the International Roaming rates tabhttps://www.virginplus.ca/en/support/international-roaming-rates.html Greece and the UK are both listed as countries Virgin mobile customers can roam in.
Are you able to test the SIM card in another device to confirm if you see the same issue. If the SIM works without issue, your device may be the issue. What kind of device are you using?If the SIM card does not work in another device, I would suggest...