Samsung — defected piece of samsung galaxy s4 mini

Address:

Mumbai City, Maharashtra

I had puchased a samsung galaxy s4 mini on 6th november 2013.Its iemi number is [protected] [protected].Fom satyam electronics 4 bunglows bill number 68335.As i started using the phone there was an network drop problem.How can there are such problems in new mobile phone? Due to this this i had to face many problems.I have given the phone in the samsung service centre in Andheri west.If a person have to use a defected piece why do we buy such costly phone. please try to replace my phone because is there any guarantee that this phone would not give me any trouble in future.please do the needfull and help me out as soon as possible.