if you want an app for online transactions then PhonePe is the best app for transaction, many other apps are also available on the play store but this app is the best. I only use this app. The thing I liked most about this app is that they are directly linked to our bank account.
The PhonePe app is a very bad app. I suggested you not to use this app because they blocked my account, without any reason, i guess. I do not know why they do this. Now I use only Google Pay.