Remove role and assign subscriber role to the user or membership cancel

code.php

<?php

add_action( 'ms_model_event', 'my_event_handler', 10, 2 );
		
/**
 * Handles an event and process the correct communication if required.
 *
 * @param  MS_Model_Event $event The event that is processed.
 * @param  mixed $data The data passed to the event handler.
 */
function my_event_handler( $event, $data ) {
	$member = false;
	$subscription = false;
	$membership = false;
	
	switch ( $event->type ) {
		case MS_Model_Event::TYPE_MS_CANCELED:
			// A membership was cancelled - either by Admin or by the member.
			// No more payments will be made but member has access until current period ends.
			$subscription = $data;
			$membership = $data->get_membership();
			$member = $subscription->get_member();
			assign_default_role( $member->id );
			break;

		case MS_Model_Event::TYPE_MS_DEACTIVATED:
			// A membership was permanently deactivated. Member has no access anymore.
			$subscription = $data;
			$membership = $data->get_membership();
			$member = $subscription->get_member();
			assign_default_role( $member->id );
			break;
	}
	
}

function assign_default_role( $user_id = 0 ){
	$user = new WP_User( $user_id );
	$user->set_role( 'subscriber' );
}