My mom and i were travelled to France with a Matrix Sim Card so that we could be in regular touch with dad. But when we landed and inserted the sim card to make calls, it didnt respond at all. After several trial and errors, we ultimately called the customer care hoping that they cud help. The man behind the phone was really understanding and he actually inquired what handset we were using and took us through the process of activating the international roaming and all. Sigh of relief!! Post that for the entire trip, we didnt have to make any calls to them. Excellent services must say!