Whether it's dealing with an online dating account or returning a work call from your personal phone, some times you just don’t want to reveal that you are the caller. It's not complicated, and fortunately, there are several ways to do this for both Android and iPhone devices. So, regardless of the mobile operating system, it is possible to make calls in secret so that the person you are calling cannot see who is trying to contact them. Instead of the mobile number, your screen will show "Hidden Number", "Unknown" or "Hidden Call".
Hidden number calling
To make a single call with a hidden number all you need to do is write the prefix #31# (for Spain) before dialling the phone number of the contact you want to call. For example, #31#12345678. This way, your phone number will not be displayed but the receiver will receive the call. He will not know who it is until he picks up the phone.
Call with hidden number by default
If you want to call with a hidden number permanently, then the method of doing so also changes.
When using an iOs, you will have to access Settings → Phone → Show Caller ID. In order to hide your caller ID you will need to disable this option by activating the permanently hidden mode. If you want to return to showing your number, you just simply follow the same steps and select "Show Caller ID".
On Android the way to do this is similar. You'll need to access Settings → Advanced Device Features → Show My Caller ID → Hide Number. In the same way as in iOS, if you want the phone number to appear again on your contacts' screen, you simply follow the same instructions and select "Show Number".
You can also contact your mobile service provider and ask them to hide your number permanently. This method may incur some expense and may not be available in every country, but it is worth mentioning as it is the most reliable method of completely hiding a number even for those who use applications that allow unknown or hidden numbers to be displayed.
There are also even more temporary solutions such as using tools that simulate hidden phone numbers, such as temporary or expired emails. Burner (available both in the browser and as an app for iOS and Android), allows you to use 20 minutes of conversation and 60 text messages for a week for free, but then you need to buy credits to extend the service and buy new numbers. You can even use it to send photos, using Picture Burner.