Hello @AnandKiran and welcome to the Community. Fitbit doesn't offer battery replacement service. The Surge is a little unique among Fitbits. I have seen instructions and videos online that show how to replace the Surge battery. But you need to know that Fitbit put the Surge on its list of legacy devices in 2020. There is no guarantee that you will be able to add it back to your account if you replace the battery.
Laurie | Maryland
Sense 2, Luxe, Aria 2 | iOS | Mac OS
Take a look at the Fitbit help site for further assistance and information.
There are companies that sell a kit to replace the battery, some will replace the battery if you send it the unit. They also have replacement bands, which are glued on.
My app still gives me the option to add a Surge. I even have the option to add the recalled Ionic, of which I located mine last week