Haier mobile vtrendy/virgin mobile, mobile store
Warranty, they charged me for replacing handset under warranty period

I have purchased a handset from mobile store haier v trendy with virgin connection, its display stopped working within a month and i went to service centr of haier mobile they told to come after three days, when i went there they gave me a replacement certificate and told to take it to the store from where i purchased my mobile and my mobile will be replaced, so i went to mobile store, they replaced my mobile after i went there two three times but charged me rs 90 telling that now the new handset cost rs 90 more than what it cost when i purchased it, i think this is un fair please help me out i have given rs 90 as i was in urgent need of mobile