The problem goes back to the time Virgin decided to run their own core network. Prior to that EE ran everything including roaming, afterwards EE just supplied signal (now Vodafone)
Being a Virtual network with no masts of their own they could not negotiate roaming agreements with foreign networks as they had nothing to offer them.
To get round this Virgin entered into an agreement with a network in Belgium to supply roaming facilities.
The problem is the Belgian network sees all +44 numbers as UK and does not differentiate between UK, the IOM and the Channel Isles.
Virgin tried to get round this by equipping their SIM with a SIM Toolkit, where roaming can be selected as Automatic, National and International. Sadly, this is a none standard arrangement and sometimes the phone can't pick up the Automatic setting. Usually, when this happens going into SIM Toolkit and manually selecting International restores roaming in places like the IOM.
The likelihood of this changing is receding as it looks certain that Virgin Mobile will be brought into O2's system in the future.
Personally if I travelled to the IOM a lot I would not be using Virgin. Use a network like Vodafone who have their own roaming agreements and also have the IOM listed in inclusive allowance.
Whatever the team say on here, how many SIM swaps and reboots they go through. IOM roaming will always be hit or miss.
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