Purchased a mobile but not at all working and company is refuing to replace

Location/place: Haridwar

Name of company/service: Sony xperia

I had purchased a sony xperia mobile woth 15 thousand but after using it for twenty days it ha never worked well. i have also got it repaired for two times but still the problem persists.
company is refusing to either replace it or refund my cash back.
please guide me what to do.
the product is being purchased just three month ago.