# Normalization of incoming phone number
When connecting multiple providers to MikoPBX, you may encounter situations where customer phone numbers come in different formats:
* In 7-digit format - **2293042**
* With a "+" sign, for example, **+79257184444**
* With "8", for example, **89257184444**
There is a need to standardize all these formats.
1. Go to the **Routing** → **Telephony Providers** section. Open the provider's account for editing. Copy the **Provider ID** from the address bar, through which subscribers call your company. Please note that in our example, we are using **a single** provider. If you have multiple providers configured, you need to perform the following steps **for each provider**.
In our example, the Provider ID looks like: **SIP-1687941868**
Provider ID
2. Go to the **System** → **System file customization** section.
System file customization section
2. Open the configuration file **extensions.conf** for editing.
extensions.conf file
3. Add the folowwing code in the end of file:
{% code fullWidth="true" %}
```php
[SIP-1687941868-incoming-custom]
exten => _.!,1,NoOp(---)
; Remove the plus sign
same => n,Set(CALLERID(num)=${REPLACE(CALLERID(num),"+")})
; For an 11-digit number, remove the first digit and add 7
same => n,ExecIf($[ ${LEN(${CALLERID(num)})} == 11 ]?Set(CALLERID(num)=7${CALLERID(num):1}))
; For a 7-digit number, add country code 7 and area code 495
same => n,ExecIf($[ ${LEN(${CALLERID(num)})} == 7 ]?Set(CALLERID(num)=7495${CALLERID(num)}))
same => n,return
; If the caller's number starts with 886142 (11 digits), remove the city code "886142"
exten => _.X!/_886142XXXXX,1,Set(CALLERID(num)=${CALLERID(num):5})
same => n,return
```
{% endcode %}
In the code above, you need to create the context with the correct name.\
Format for creating the context:
```php
[ID-PROVIDER-incoming-custom]
```
* **ID-PROVIDER** - the value you saved in the first step of this instruction. In our example, it's **SIP-1687947415**.
Code for extensions.conf
{% hint style="danger" %}
Please note that if you have multiple providers in MikoPBX, you need to create the code fragment above for each provider, taking into account the uniqueness of each provider's ID.
{% endhint %}
If you want to add normalization for all providers at once, you can create the "add-trim-prefix-clid-custom" context. For example, to add a "7" to all 10-digit caller IDs:
{% code fullWidth="false" %}
```php
[add-trim-prefix-clid-custom]
exten => _.X!,1,ExecIf($[ ${LEN(${CALLERID(num)})} == 10 ]?Set(CALLERID(num)=7${CALLERID(num)}))
same => n,return
```
{% endcode %}
