BlackBerry 8520
Battery getting discharged within 4-5 hrs even at stand by mode

I am akanksha gupta. I have bought Blackberry 8520 on 16th july from Sangeetha Mobile store at Mantri mall. After one month i started having problem with its battery. It is getting discharged after every 5 hrs even at stand by mode.

I have lodge a complaint to vodafone (mr. Sunil- 9886685272) but they are not replying.

i have never such kind of bad customer service from blackberry and vodafone.

Please solve my problem