Please note that the GeoSIM will only work in an unlocked mobile phone handset.
An unlocked handset means that your phone will work regardless of which mobile operator's SIM you put in it. Most handsets are sold locked to a particular network. Unless you have unlocked your handset or you purchased it "SIM FREE" or unlocked, it is highly likely that your handset is locked to your current network.
Anecdotally we have heard that O2 handsets are not locked - however we cannot guarantee that this is the case.
To check if your handset is unlocked, insert a SIM card from a different network than the network you currently use. For example, if you have a T-Mobile phone/SIM, try putting an Orange or Vodafone SIM card in to your handset. If the phone will alow you to make outgoing calls with an alternative SIM inserted, then your handset is already unlocked. This means the GeoSIM will work in your handset - provided you have a compatible handset of course. If it does not work, then you will need to get your handset unlocked.
To unlock your phone you can either:
Buy a GeoSIM global SIM card, insert it in your phone and start saving on your calls!