You can close the webview without starting the next passage by using the Smooch or Facebook API calls, depending on your integration.
If you want to close all webviews regardless of the channel, see Close all webviews.
Smooch
window.WebviewSdk.close()See https://docs.smooch.io/guide/conversation-extensions/
MessengerExtensions.requestCloseBrowser()See https://developers.facebook.com/docs/messenger-platform/webview/#messenger_extensions