What a VPN does not hide in a city

A city network can include cameras, number-plate readers, and Wi-Fi or Bluetooth equipment that notices a phone nearby. None of that depends on the websites you open. A VPN does not switch those off.

What a VPN does change is the traffic from an app that is connected through it. Websites and the local network then see an encrypted tunnel and the VPN server's address, not the address your phone was given on that hotspot.

If the phone is probing for Wi-Fi networks, or an app is using location services, that happens outside the tunnel. Turning those off is a phone setting, not a VPN feature.