Uber India — I was overcharged-cash transaction

Address:

Bangalore, Karnataka

I have paid more amount (120) than the billing amount (91). I have raised an issue but I have been told that as it was a cash transaction, the money cannot be refunded.
It is a pure cheating case. Please stop this type of corruption. The amount is not very big, but the reply is worst. I can't believe a renowned company like Uber can't provide a service and where cash transaction doesn't matter at all. I will take necessary steps against it if I don't get my refund.