If your device has signal bars, your device and the SIM card are working.
Please check :
* Mobile data is turned ON in the settings
* Airplane mode is OFF in the settings
* APN values (values has to be in small letters. No capitals )  APN setting page

For iPhone and some androids, the signal bar may be shown as 0. If that is your case, please ignore it.

For other cases, please contact us