Ample Technologies — network issues after battery replacement

Address:

Bangalore, Karnataka, 560050

Hi,
I have started to face network issuse immediately after opting for battery replacement scheme. My phone worked all fine before that, because of your service centres faulty service i am unable to use my phone. When i visited the service centre at mantri mall they just washed there hands off and asked to pay for diagnosis and service charge. My phone was working fine and it was not tampered that why you accepted it under battery replacement and after replacement when inam facing network issue you are telling device is out of warranty and i will have to pay service charge?
Please tell me why should i pay for your faulty service.