Automatic subscription upgrade without actually completing subscription process

When an existing member selects the 'upgrade' button of another subscription it automatically changes that members subscription without the user actually following the subscribe prompts and going through paypal. Is there a way to keep the user at their previous subscription until they complete the entire subscription process (i.e. pay through paypal). I've checked and it displays this new subscription level both on their subscription page (frontend) and on the dashboard end. I do not have a live site yet to show you, unfortunately.