Nokia N8 — Battery getting discharged in 2 hrs

Address:

Rangareddy, Andhra Pradesh

i have bought Nokia n8 last month of 10th i have used it 20 days and i went for upgrading for symbion Anna s/w trough the Nokia care they have given ofter upgradation and went to my home mobile charged full battery while using internet all of sudden ofter 30mins battery got discharged to 2points
again i tested same i did battery fully charged again getting same problem battery low then i went Nokia care they said we will observe it for 24hrs they given phone back to me they said its working fine then i went home again i checked same problem occurred and i went Nokia care again they took phone they said we will send this phone to Nokia head office Delhi ofter 10 days it came back to me again i observed again same problem like that i went Nokia care total 5 times there is no result why Nokia service not replacing phone i dint understand such a big company they can replace bcoz i spent lot of money to buying n8