Hi
When you say the service centre I am assuming you are talking about apple support/apple store
There are lots of good ways to extend they battery life of your iPod touch such as
Closing apple that are running in the background
Turing down your brightness
Turing your Bluetooth off when not in use
Turning off background app refresh
If the above doesn’t help and apple isn’t doing anything else you could replace the battery but that would void your warranty and it’s not a easy task
I would go to apple again before we do any repairs ourselves as we want to keep our warranty intact
Hopefully this helps
Any questions please ask
Thanks:-)