This action is used to do action directly before user's plan is changed OR new plan is added in plan list.

Hook Type: Action
Source: core/classes/class.arm_subscription_plans.php
add_action( 'arm_before_change_user_plans', 'your_function', 10, 4);
function your_function($user_id=0, $old_plan_id_array = 0, $new_plan_id = 0, $new_plan_object) {
     //Do Your Action
    //$user_id User ID.
    //$old_plan_id_array Array of user's old plan IDs.
    //$new_plan_id Plan New plan ID. 
    //$new_plan_object New Plan Object. 
User ID
Array of user’s old plan IDs
New Plan ID
New Plan Object