Cello — no replacement/ no repair even under warranty

I am keerthi ajay from bangalore, i have purchased a 1000ml cello flask from flipkart on 6th october, for the first few days it was functioning normally like the hotness of water was lasting for around 8 hours.. But now for the past two weeks it's like the hotness is lasting for just two hours and the water is turning to cold completely, so wen i mailed the cello team on [protected]@celloworld.com they asked me to sent pictures if flask including bottom side.. I sent and they asked me to sent more pictures of the bottom of the flask. Again i took and sent the bottom pictures.. Today morning i got a mail from them saying there's a dent on the bottom side that's y it's not functioning properly they can't help with that... I should say it's just a negligible scratch i already saw at the time of purchase and the flask was ok for few days too.. Now all at a sudden from where a new deformation came??? They are saying soo many excuses they can so no need to replace or atleast repair since my flask is having warranty... A girl to whom i talked and was so called the superior of the first girl was talking so rudely that she doesn't bother at all.. The number is : [protected].. She don't even give minimum respect to her customers.. If they cannot replace y can't they repair??? Cello is such a fraud team that they never replace their product if it's under warranty too they will say they have find a dent so they cannot replace. Really?? Cello has such a cheap quality less products?? That it will stop working with a negligible small scratch...??