Pre-subscribe a wallet, then activate it with an OTP (master 123456 in mock/sandbox).
Look up a wallet by contract id (balance/history) or phone (profile).
Credit a wallet. No OTP step.
Debit a wallet. OTP is auto-fetched in mock/sandbox.
Move money between wallets. On-us credits the recipient wallet if it exists locally; off-us marks the recipient as external.