very poor service of my vostro 3500 laptop

It is very bad to treat to a customer. they don't doing anything for their customer except asking stupid questions each and every day. am experience badly with my laptop from begining . they changed my hard disc , motherboard 2 times now having issue with battery charging, they said issue with battery and i changed with new one and issue is the same. even i informed to the service portal they not sending any technical person to check it out even my system in under pro service warranty. it is not acceptable