punch in *67 before entering the number; it works on Android and iPhone.
For example,*675555555555.
This works even if the other person already has your number in their phone.

*67 does not work when you call toll-free numbers or emergency numbers.
Tap thethree-dotmenu at the top of the app, next to the search bar.
TapCalls, orCalling accountson some devices.

If you don’t see that, first select your phone provider.
TapHide numberwhen the pop-out interface is displayed.
Not all carriers support this feature.
If yours doesn’t, there areother ways to make your number private on Android.
Scroll down and choosePhone.
In theCallssection, tapShow My Caller ID.
Why Use *67?
Check with your phone company if a particular code isn’t working as expected.
FAQ
Yes.
Tosend anonymous textson an iPhone, go toSettings>Phone> turn offShowMy Caller ID.
Next, tapCaller ID>Hide Caller.
Toblock a number on an iPhone, launch thePhoneapp and tap theRecenttab to show recent calls.
Find the number you want to block and tap thei.
SelectBlock This Caller>Block Contact.
Or go to yourContacts, tap a contact >Block This Caller.
To block a number on Android, launch thePhoneapp and find the number you want to block.
(On a Samsung phone, tapDetails.)
If your carrier supports blocking, you’ll see an option toBlock numberorReject call.