Global system for mobile communications (GSM) providers lock the subscriber identity module (SIM) in their phones to prevent you from accessing other GSM networks. This is standard practice in the mobile industry. While many Internet retailers will sell you an unlock code, many cell phone users don’t realise that they can get a free unlock code from their mobile providers. If you have an account in good standing for more than a couple months, most GSM mobile providers will honour a SIM card request at no charge.
Dial *#06# from your Sony Ericsson 750i handset. Take note of the international mobile equipment identity (IMEI) number. Write it down for future reference.
Contact your GSM mobile provider to request your SIM unlock code. Give the representative your IMEI number when asked. Provide a valid e-mail address so that the company can send you the SIM unlock code and instructions once they get it from Sony Ericsson.
Open the email from your GSM mobile provider that contains the SIM unlock code and instructions. Write down the SIM unlock code for future reference.
Slide the battery cover off the back of the Sony Ericsson 750I handset. Slide the SIM card from its holder. Replace it with a SIM card from another GSM mobile provider, making sure that the gold contacts are facing down and the cut-off corner is aligned correctly. Replace the battery cover and turn the handset back on.
Click past the error message stating that the SIM card is not compatible with the phone. Enter the SIM unlock code on the next page in the fields provided. Click “OK.”
While most GSM mobile providers offer free SIM unlock codes to customers who have had their phones for over a few months and have no balance on their accounts, criteria can vary. If you have any doubt that you qualify for a free SIM unlock code, contact your GSM provider’s customer service.