I have been using Paytm for a couple of years now and always wanted to mention it to them that they can add a feature to assist users if they make wrong payments in error. It could be as simple as a hyperlink taking the user to an escalation matrix or an advanced feature of dialling in from the payment page to talk to the customer service representative.
As I made mistakes a couple of times with payments, I am sure there may be others willing to have something like this for an instant help.