Pay in a general way is really bravo. Text is ok while email is just too old-school.
Highly recommended: Why not Create another brand new app to have everyone into it thus everyone could have chance to receive and send money easier. Example: PayMe from HSBC (https://payme.hsbc.com.hk/personal).
In text: 1. Why not consider iMessage app for iOS users, good examples: Venmo, Cash app, or even Apple Pay Cash (US);
2. Embedded into other msg apps, like WhatsApp, Messenger,…;
3. Payment should be easier. Letting your customers’ friends enter his/her bank account again and again is really a bad experience when they receive money (It’s impossible for everyone to remember bank details)? Look forward to a more universe way.