Remove a network

Try Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings.

Hi jnet57uk, thank you for posting in Apple Support Communities.

Can I suggest that you update to the latest iPadOS which is 15.2.1 (if you have not done this already) as updates can help resolve some problems. The following link can help you:

https://support.apple.com/en-au/HT204204

If you do not have the option to forget the networks as per the following link:

https://support.apple.com/en-au/HT208941

and you are not using a supervised device which the following may help:

https://support.apple.com/en-au/HT202837

Can I further suggest you contact Apple Support as follows:

• Online:--> Genius Bar Reservation and Apple Support Options - Apple;
• Contacting a local Apple Store or AASP among the list provided above but also again as follows Apple – Location Selector; or
• Using the "Apple Support" app, available and downloadable from App Store. 

jnet57uk Said:

"Remove a network: Don’t have the option to forget network on previous network"

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Performing this Correctly:

What steps are you taking to perform this? You may be performing this incorrectly. Reply with the steps you are taking.

The ability to forget a network is only available when you are in range of the network so you can see if on the list, and you have joined the network in the past. If you have never joined it, you will not have the option to forget it, you will just see it listed if you are in range of the network.