As per one of the studies conducted, State Bank of India (SBI) was the most popular for online transactions. You can read about the RBI – Reserve Bank of India [UPSC Indian Economy Notes] in the given link.

Further readings:

Related Links
RBI Grants Licensing for Small Finance Banks: Notes for UPSC Current Affairs	Bad Banks – Idea Proposed by Indian Banking Association (IBA) Due to COVID-19
Consumer Price Index (CPI) – CPI and its Types [USPC Indian Economy Notes]	Bank Rate – Definition, Calculation: Notes for UPSC Indian Economy
Inflation in Economy- Types of Inflation, Inflation Remedies [UPSC Notes]	Monetary Policy Committee – Objectives, Structure