How do I turn off Security Delay on iPhone?

See the pic below which is self-explanatory

Probably you have "Always" Ticked in place of "Away from Familiar Location"

For enhanced security, there's a one-hour delay when changing your location settings from "Always" to "Away from Familiar Location." This applies even if you use Face ID for authentication.



A delay will be required when you are not at a familiar location, such as your home or work, to change security settings.

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