Here's an easy way to reduce the bandwidth of your mobile data while saving you some money if you mainly use your phone for instant messaging or email checking. If you use heavy multimedia content on mobile data then this will just frustrate you. This method can easily be reverted to full bandwidtch.
First step is going to Settings, more Networks.
Step 1: Lower Speed for Lower Usage!
Following the screenshots, I opted for the plain GSM mode to send instant messages. Also when I have poor signal reception, this option somehow keeps the data connection alive to let basic messaging through. It is quite handy!