Sunyu9 - Phone Number Migration App
Overview
Sunyu9 helps people in The Gambia move their phone contacts from the old 7-digit numbers to the new 9-digit format. It scans the phonebook, finds numbers that still use the old format, shows every proposed change, updates the contacts you approve in bulk and lets you undo. Contacts never leave the phone: there is no account, no server and no network calls.
The Challenge
When The Gambia moved to 9-digit phone numbers, people were left with hundreds of contacts in the old format. Updating them by hand is slow and error-prone, and handing your whole address book to an online tool isn't an option for most people.
The Solution
Built a conservative numbering engine (normalise, validate, classify, convert, re-validate) that only touches numbers it is sure about and explains every number it skips. Before writing, each affected contact's full original and new phone list is saved locally, persisted every 20 contacts so even an interrupted run can be undone exactly. Backups can be exported as CSV through the share sheet.
Screens
Outcome
The full flow works end to end: permission, scan, preview, confirm, write with backup, and success with Undo, Retry failed and Save backup file. The backup survives app restarts so Undo stays available later from Settings.
Key Results
Tech Stack