The SBI app getting downloaded by 500+ users is very suspicious to me. They have one of the worst UI in apps, have you tried using the YONO app? Nothing works on that app as they claim.
YONO is pretty bad and I used them too because SBI as my first bank account like most of the Indian residents and 6/10 times the payments will be failed due to server error and for a government bank with such large userbase not given proper resource like HDFC or ICICI do.
But for the record it is the official erupee wallet app from SBI.
eRupee by SBI