through wifi i can receive whatsapp notification normaly but through 3g i can't, what do you think the problem is?

Dear sirs,

I'm facing a problem with whatsapp notification.

- If my device work through wifi, than I can receive whatsapp messages normally even if my device is logged off.

- If my device work through 3G, than I can't receive any whatapp notification unless the device is logged on and the whatsapp application also.

some people advice me to remove the software and reinstall it again. I did it but the problem still the same.

Best Regards

Samir Choucair