Turn off whatsapp in Nokia E71?

Hi, Whatsapp is a great app. However, I could not switch it off in order to save my battery. If I switch 3G off, then it will be automatically on for running whatsapp. Is there anyone who experienced this problem before? could you give me some tips please? Thanks in advance!

same problem here... no solution yet! Cause you can't switch mobile internet off, nor the app!! uninstal only solution but no option if you want to use the program :p