Use this code example to target a specific payment action ID and send an email if payment is marked as complete.

add_action( 'frm_payment_status_complete', 'frm_trigger_action_payment_complete' );
function frm_trigger_action_payment_complete( $atts ) {
	$target_action_id = 450; // change 450 to your payment action ID
	if ( $atts['payment']->status == 'complete' && $target_action_id === (int) $atts['payment']->action_id ) {
		$to      = get_option( 'admin_email' );
		$subject = 'Payment complete';
		$body    = 'Payment made for $' . $atts['payment']->amount;
		$headers = array( 'Content-Type: text/html; charset=UTF-8' );
		wp_mail( $to, $subject, $body, $headers );
	}
}

Use this example to change the user role when the payment is completed. With a recurring payment, this hook will be fired each time a payment is completed.

add_action( 'frm_payment_status_complete', 'frm_change_the_role' );
function frm_change_the_role( $atts ) {
  $new_role = 'contributor'; // change contributor to the new user role
  $entry = isset( $atts['entry'] ) ? $atts['entry'] : $atts['payment']->item_id;
  if ( is_numeric( $entry ) ) {
    $entry = FrmEntry::getOne( $entry );
  }

  $user_id = $entry->user_id;
  if ( ! empty( $user_id ) ) {
    $user = get_userdata($user_id);
    if ( ! $user ) {
        return; //don't continue if user doesn't exist
    }

    $updated_user = (array) $user;

    // Get the highest/primary role for this user  
    $user_roles = $user->roles;
    $user_role = array_shift( $user_roles );
    if ( $user_role == 'administrator' ) {
        return; //make sure we don't downgrade any admins
    }

    $updated_user['role'] = $new_role;
	
    wp_update_user( $updated_user );
  }
}