Ducting Ac not working after one year

I have purchased ducting ac before one year ago. Now this ac not working properly and have too much noise. Now when I call to customer service center of company then they told me this noise is normal & cooling after one year is decrease and you need to topup your ac gas. But within one year how its possible to topup gas. But they give me too much excuse not solution. Please beware from this. Becuase I bought it in 300K . Now I feel loose of my money.