Move PMPro members to another level when they cancel.

pmpro-cancelled-level.php

<?php
/**
 * By default cancelled members are changed to level 0. This recipe changes that behavior to give them a "cancelled" level that 
 * you have created for that purpose. Can be used to downgrade someone to a free level if they cancel.
 */
/**
 * [pmpro_after_change_membership_level_default_level description]
 *
 * @param  [type] $level_id [description]
 * @param  [type] $user_id  [description]
 * @return [type]           [description]
 */
function pmpro_after_change_membership_level_default_level( $level_id, $user_id ) {
	// if we see this global set, then another gist is planning to give the user their level back
	global $pmpro_next_payment_timestamp;
	if ( ! empty( $pmpro_next_payment_timestamp ) ) {
		return;
	}

	if ( $level_id == 0 ) {
		// cancelling, give them level 1 instead
		pmpro_changeMembershipLevel( 1, $user_id );
	}
}
add_action( 'pmpro_after_change_membership_level', 'pmpro_after_change_membership_level_default_level', 10, 2 );

This recipe is included in the blog post on "Change Membership Level on Cancellation or Expiration" at Paid Memberships Pro here: https://www.paidmembershipspro.com/change-membership-level-on-cancellation-or-expiration/