Easy GSM and Short codes Down below there is an overview of a few GSM codes to use for some of our services. You will have to call to the codes provided here, once you want to use the services attached for the codes. Related articles How does Voicemail work? Why is my sim card not working? Troubleshooting network signal issues How can I renew my data plan? Is there a fee for converting from Prepaid to Postpaid?