Connectivity issue on Apple CarPlay

When I using the Apple car on my Kia Sportage car, the iPhone connects to the Apple car via WiFi . So far so good …

The problem is that the WiFi signal stays on… and the phone is trying to get data from the Apple car instead of using cellular data .

if I close the WiFi connectivity and turned it on again , the iPhone is disconnect and reconnect .. but when it reconnects the problem is no longer exists … the phone is connected via WiFi to the Apple car but data comes from cellular connectivity

the problem starts only couple of days ago after I upgraded to the last version 18.1.1.

is there away to tell the iPhone in advanced that when it has WiFi connectivity but no data available , it should use the cellular data?

[Re-Titled by Moderator]