Redirect away from the level page if you don't have a required level with Paid Memberships Pro.

my_template_redirect_upgrade.php

/*
	Redirect away from the level page if you don't have membership
*/
function my_template_redirect_upgrade()
{
	global $pmpro_pages, $pmpro_level;
	
	if(empty($pmpro_pages))
		return;
	
	$member_level = pmpro_getMembershipLevelForUser();
		
	if(is_page($pmpro_pages['levels']) && pmpro_hasMembershipLevel() && !pmpro_isLevelExpiringSoon($member_level->ID))
	{
		wp_redirect(site_url());		//change redirect url here
		exit;
	}
}
add_action('template_redirect', 'my_template_redirect_upgrade');