I use paytm more than year. I can do multiple thing just like shopping , mobile recharge, dth recharge etc. After all that you can use promo code to get an attractive discount / offer for your product.
For example when I need to recharge my mobile, simply just recharge with your atm card. ( it will save your time and petrol to go shop)
And if you use promo code ( please check the expiry of every promo code ) then you you will get cash back which is simply used in mobile recharge of any operator.