Is there a VPN service that automatically turns off mobile vpn when connected to wifi?

Question

VPN

Good evening!
On my own I could not master the solution of the problem, I ask for help from experts.
We are talking about paid vipian services , an iPhone and a zyxel Keenetic Omni II router.
Convenient:
Many vipian services have a mobile application that is convenient.
Many vipian services can be configured in such a way that not a separate computer will connect to them, but a router, and then all devices connected to the router will be under vipian, this is also convenient.
Not convenient:
When a mobile phone connected to the vipian connects to a router that is also connected to the vipian, it will result in a double vipian on the mobile device, which is slow.
Question:
Please tell me which of the services, and how you can configure it in such a way that the mobile phone, when connected to Wi-Fi under Vipian, turns off Vipian in the phone, and restores it back in case of disconnection from Wi-Fi. I apologize for the crooked explanation, I tried my best :-)
Additional question:
Recently, it has become more and more difficult to find a service that allows you to configure Vipian on a router.
Please tell me what services will be possible to set up

Answer 1

tasker.dinglisch.net/download.html
if IOS - then God himself ordered to pay

Answer 2

Can you please tell me what task Tasker solves?