Blocking Numbers
Call Manager makes it possible to block calls from specific Public Switched Telephone Network (PSTN) numbers, whether the source is Microsoft Calling Plans, Direct Routing or Operator Connect. Numbers blocked using this feature are blocked for the entire Microsoft tenant. The caller ID of every incoming PSTN call to the tenant is checked against the blocked list for a match. If a match is found, the incoming call is rejected.
Block Number from Call Log
Navigate to the Call Logs using the left side menu. Select the call log entry from the caller you wish to block.
This will open a modal that prompts you to confirm. Blocks added by mistake can be removed, but the changes upstream in Microsoft's call handling are not instantaneous, a number blocked by mistake can remain blocked whilst the changes propagate.
Once the Block button is pressed you will get confirmation that the number block has been created. This can take a while to become effective, typically 10 minutes or less is sufficient.
Managing Blocked Numbers and Patterns
Call Manager provides a blocked number management page. This is available from the left hand side menu under Numbers > Blocked Numbers.
The top toggle on this page is a global switch to enable/disable the number blocking functionality.
Blocked Numbers and Number Patterns lists each individual block pattern. A pattern can specify a specific number, or it can match on multiple numbers. Blocks created from the Call Log page will only match the single Caller number.
All blocks make use of patterns, which are simplified regular expressions. For those new to regular expressions (often referred to as 'regex'), it is helpful to know that:
^ anchors a pattern to the start of the string
$ anchors a pattern to the end of a string
\+ matches a literal '+' character. The plus character is a special character in a regex, which is why it is escaped in the examples below.
In the screenshot above we have two blocks:
- The first rows uses the pattern ^\+11234567890. Because there is no $ character at the end of the pattern, this will match +11234567890, but also any caller ID that starts with that number, e.g. +112345678901 (an additional 1 at the end).
- The second row uses the pattern ^\+447927000000$. As this pattern has anchors at the start and end of the string it will only match a single number, which is +447927000000
Deleting a Number Block
To remove a block from a number, navigate to the Blocked Numbers page via the left side menu. Find the appropriate pattern and click the red trash icon at the end of the row. Changes to patterns do not typically take place straight away, allow some time for the change to propagate in Microsoft's systems.
Check If A Number Is Blocked
The Test Number Blocking section on the Blocked Numbers page allows you to enter a number and see if Microsoft will block the call or not. This can be helpful to confirm if a new block is active yet, or whether a disabled/removed block has stopped being active. This can also be helpful where you've added a block that matches several numbers and want to ensure the pattern is correct.
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