autodropsub

<?php

function custom_remove_from_free_subscription( $tosub_id, $tolevel_id, $to_order, $user_id ) {

    // check for the subscription id
    if( $tosub_id == 3 ) {
        // It's the one we are interested in
        // Get the member
        $member = new M_Membership( $user_id );
        // Check they are on the free subscription
        if( $member->on_sub( 5 ) ) {
            // Remove the subscription
            $member->drop_subscription( 5 );
        }

    }
}


add_action( 'membership_add_subscription', 'custom_remove_from_free_subscription', 10, 4 ));

?>