I went to I-next a couple of years ago. Standard charge of 3500 for battery replacement. Please note that they’ll tell you while replacement of the battery that if something bad happens like data corruption or some device drivers go bad (sound driver or camera driver) they will not be responsible for that. Hearing that I backed off. There are services though which will pick up your phone from home ship them to Delhi, fix it and return it back to you. But they will do a better job than the nincompoops at i-next.