> For the complete documentation index, see [llms.txt](https://docs.mikopbx.com/mikopbx/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mikopbx.com/mikopbx/english/faq/cases/bluring.md).
# Hiding the Caller’s Number from Employees
In some cases, employees should not see the actual phone number of a client. Here is a possible approach to solving this problem: employees will be provided with an alternative number that they can use to call back.
1. Go to **System** → **System File Customization**.
"System file customization" section
2. Open the **modules.conf** configuration file for editing. Set the mode to "**Add to end of file**".
"Add to end of file" mode
3. Connect the module to calculate the hash sum:
```
load => func_md5.so
```
4. Open the **extensions.conf** configuration file for editing. Set the mode to "**Add to end of file**".
"Add to end of file" mode
5. Define the context for number substitution:
{% code fullWidth="true" %}
```php
[dial_create_chan-custom]
exten => s,1,NoOp()
; Only for incoming calls
same => n,ExecIf($["${CHANNEL(channeltype)}" == "Local" || "${FROM_DID}x" == "x"]?return)
; No processing required if an internal number is calling
same => n,ExecIf(${DIALPLAN_EXISTS(internal,${CONNECTEDLINE(num)},1)}?return)
; No processing required if the number is not in the list
same => n,ExecIf($[${DIALPLAN_EXISTS(bluring-extensions,${CHANNEL(endpoint)},1)} == 0]?return)
; Retrieve the cached number
same => n,Set(blNumber=${CONNECTEDLINE(num):-4}*${MD5(${CONNECTEDLINE(num)})})
same => n,Set(DB(bluring/${blNumber})=${CONNECTEDLINE(num)})
; Replace the caller ID
same => n,Set(CONNECTEDLINE(num)=${blNumber})
same => n,Set(CONNECTEDLINE(name)=${blNumber})
same => n,return
```
{% endcode %}
6. Describe the context with the numbers for which you need to replace the number:
```php
[bluring-extensions]
; Allow number substitution for extension 201
exten => 201,1,NoOp()
; Allow substitution for all four-digit extensions
exten => _XXXX,1,NoOp()
```
7. We will provide the opportunity to call back to a replacement number:
```php
[all_peers](+)
exten => _XXXX*.,1,Set(number=${DB(bluring/${EXTEN})})
same => n,ExecIf($["${number}x" == "x"]?hangup)
same => n,Goto(all_peers,${number},1)
```
---
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