small thing but a big issue.

i bought 20 recharge vouchers of reliance gsm, each of price 29 rupee.1 GB 3G data with 7 days validity was applicable as per the scheme. but suddenly company has chenged it and now the same voucher gives me 100 MB 3G data for 7 days.the last date to recharge the voucher is november 2017 then how can they changed it suddenly. i know its a small thing but still as consumer i feel cheated.