@Regression

 Many thanks for your feedback

We tested on the IOS that with Kasa app 3.0 you can still manage the device locally even Wifi network has no internet, 

As recently learned of from our team, for the purpose of local device security and brand development, the Kasa App 3.0 and later versions will no longer support a guest account login, and registering a TP link ID is now required to manage your kasa devices.

TP-Link ID determines that only an authorized user with account information can access your local devices via the app. After logging in with a TP-Link ID, per account will get the most recent firmware and security updates, as well as use some advanced functions like Smart Actions.

It is regret hear that you would like a  refund, it is recommended to reach the retailer directly and see if they could assist with that. Or reach our local support here take a look into your concerns further for your personal situation based on the warranty policy. 

Thanks for your understanding and cooperation.