Forgetting a wifi network

The "Forget This Network" option only appears while you are in range of the network in question.

Turning off Auto-Join means you will be asked if you want to connect to the network in the future, the same as if the network was unknown.

How to forget a Wi-Fi network on your iPhone, iPad, iPod touch, or Mac - Apple Support

What do you see when you click the "i" in a circle next to the network name?

That should be where the option appears if it's a network in range that you have connected to in the past.

For example, if it's a network you've joined in the past, you should see something like this:

If you have not joined it, you will see something like this:

I do not get the "Forget this network" possibility on my phone (Iphone 6S plus, iOS15.1). So what can I do?

I need to change the certificate for the work WiFi by forgetting the network and then log in again.

Are you within range of the network?

You can only forget it when it is in range.

How to forget a Wi-Fi network on your iPhone, iPad, iPod touch, or Mac - Apple Support

It is not a supported phone and it is in range of the network.

I get the lower version, even if I have joined the network before (every day at work, last time Monday this week).