The geolocation info that data providers use based on IP addresses comes from third-party databases (ie not held by Vodafone), and it's these that are increasingly out-of-date. It's a situation that is not going to get any better at least until Vodafone transition to IPv6 (they are testing this - in the usual VF slightly incompetent manner).
What can you do? Petition the data providers to get the databases updated, or better still use more reliable means to identify user locations. There is always the possibility of using a VPN (though the benefits of these are overblown).
