In most cases you can replace them yourself.
If you're confident enough to open it up, and remove the batteries you shuld be able to take them to anywhere that specialises in batteries and get some.
Otherwise, we seem to see a number of people here from India, so maybe someone is local to you.
If you are going to try it yourself, please make sure you take the obvious precautions, most importantly that the device is unplugged and switched off before you do anything. After opening the device the first step should be to remove a conection to the batter(y/ies)
