To change your default bank account, where payments are made too and from:
1. Tap Activity (bottom middle)
2. Tap Wallet (top right)
3. Tap the account you'd like to make your default
4. Toggle "Default account. Send and receive money here".
Note - only current accounts with a sort code and account number can be default accounts. Credit cards can't be the default at this time.
Enjoy ✌️