You don't understand what he is asking. He is not using it for internet, he just wants to stop it using 2.5G mode, since he is not connecting to anything deleting the APN won't have any effect.

I wasn't aware that 2.5G uses more power than 2G and I don't think there is any way to select pure 2G without including 2.5G. Maybe someone else will be able to give you a more useful answer.