In most cases — yes, but with a few caveats:
The app is carrier-agnostic, meaning it works with any carrier as long as call forwarding is supported by your original provider.
If your carrier allows you to forward calls (unconditionally or conditionally), KeepMyNumber will work.
In rare cases, some budget or prepaid carriers may restrict or disable call forwarding — making the app unusable unless the number is ported or forwarding is unlocked.
Check with your carrier or use the app’s setup guide to confirm call forwarding compatibility.