DID NOT GIVE MONEY

i purchased a mobile SONY XPERIAZ on 16/09/13 at Rs34300. After 8-9 months i went to mobile store to re-generate a bill they give me a bill Rs34000.I said i purchased a mobile at Rs34300 but you me a bill of Rs34000 then they said you have to come with a original bill if any difference in bill then i will give.Then tomorrow i go they did not give money they give excuses like you come tomorrow,today is Saturday i will not give money etc
i go many times but they give excuses instead of money
plz solve my problem as soon as possible