Ultimate Member - Make mobile number as username

Ultimate Member - Make mobile number as username

add_action("um_submit_form_register","um_090321_mobile_number_validation");
function um_090321_mobile_number_validation( $post_form ){
  
    if(  isset( $post_form['mobile_number'] ) && ! empty( $post_form['mobile_number'] ) ){
        global $wpdb;

    $wpdb->get_results( $wpdb->prepare("SELECT * FROM {$wpdb->usermeta} WHERE meta_key = 'mobile_number' AND meta_value = %s", $post_form['mobile_number'] ) );
        if( $wpdb->num_rows > 0 )  {
            UM()->form()->add_error('mobile_number', __( 'Mobile Number already registered', 'ultimate-member' ) );
		    }
	}  

}

add_action("um_user_register","um_090321_after_register_complete", -1, 2 );
function um_090321_after_register_complete( $user_id, $args ){
   
    global $wpdb;
    $wpdb->update( $wpdb->users, array('user_login' => $args['mobile_number'] ), array('ID' => $user_id));

}