You can set all incoming calls to be suppressed.
In the web/desktop client
-
Click on
settings at the bottom left.
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Under the heading "Account," click on "Privacy."
-
Check the box next to "Suppress all calls".
In iOS
-
Tap on
in the top left corner.
-
Tap your username at the top.
-
Tap "Privacy" in the first block.
-
Press the "Suppress all calls" switch.
In Android
-
Tap on
in the top left corner.
-
Tap the
icon next to your username at the top.
-
Tap "Privacy."
-
Activate the "Suppress all calls" switch.