Android devices do have a built-in ability to block these type calls. However, there is no service or application on the iPhone that can. This is a limitation of iOS and Apple has not yet offered developers this ability. However, neither device can uncover the true phone number behind a private call with RoboKiller.
The good news is that we are also the creators behind TrapCall - the world’s first and most popular service to unmask blocked calls, so you can actually reveal the number of these callers. By revealing the number hiding behind these blocked calls, you can get to the bottom of both WHO and WHY this caller is calling you and get them to stop. TrapCall has been around for over 10+ years and has over 750,000 satisfied customers, with over 14,000,000 calls unmasked!
* Please note that you can't use RoboKiller and TrapCall at the same time.