Acer — battery dead under warranty but no changing

Address:

Kurukshetra, Haryana

i bought my acer aspire laptop on 10 agust2011.
from last 20 days m facing battery problrms
the backup of the battery is only 50 min.
after that i complained about it.
but the service center says they will not change the battery.even the dont want to write my complaint .
now the battery shows a red color croos symbol on it. the notification shows to change the the battery.
my laptop is under warrenty.
but still the dont want to change the battery. they just avoiding me,

my laptop sr no. is <lxrl80c0061242c2381601> this is under warrenty
.it is under total cover warrenty.
don't buy acer
go for dell or hp