First do a recharge of 10rs u will get Rs6 as talktime and 5mb gprs plan with a validity 1 week.

Dial *126*1# and then check ur gprs balance it will show 5mb validity 1 day.

Now just recharge with 5rs gprs plan and your 50mb plan will be added to with your 5 mb plan with a validity of 1 week...

Check it by dialling*126*1#.