Sim card being used by someone else!

My mother upgraded her phone, a few days after getting a message saying that the upgrade was successful her phone lost service (the sim card stopped working). After inquiring why this had happened we were told that the sim card is still active and that the new phone has been delivered. However, we have not received the new phone and it has been active for over three days. We go to the telkom store to block the sim card and port the number to a new sim card and nothing gets done. When asking for help, they say they can not do anything as the upgrade was done by the call center, this is ridiculous service!!