A subscriber identity module (SIM) card is a removable chip that is inserted into Global Systems for Mobile Communications (GSM) cell phones. The SIM card stores identity information about the subscriber so that the GSM network can recognize the subscriber. Your mobile phone number is assigned directly to your SIM card. It is, therefore, possible to manually change your mobile phone number by purchasing a new SIM card.
Remove the existing SIM card from your cell phone. The SIM card is normally located under the battery compartment. Slide the back cover off your phone and remove the battery to locate the SIM card. If you can't locate the SIM card, consult the owner's manual for your cellular phone.
Purchase a new SIM card. GSM cellular service providers worldwide generally sell pre- and post-paid SIM cards for a nominal fee.
Insert the new SIM card into your phone to manually change your mobile phone number.