> ## Documentation Index
> Fetch the complete documentation index at: https://docs.monobot.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# PSTN
The **PSTN (Public Switched Telephone Network)** allows your system to handle real phone calls and SMS using purchased phone numbers.
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## Overview
Use PSTN when you need:
* inbound calls from real users
* SMS notifications and messaging
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## Phone Numbers
All PSTN functionality is based on phone numbers.
Each number can:
* receive calls
* send SMS (See [SMS Usage](../communication/communication))
* be assigned to a specific agent
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## Buy Phone Number
To start, you need to purchase a number.
### Steps
1. Go to **Phone Numbers**
2. Click **New Phone Number**
3. Select a **Country**
4. (Optional) Filter by digits using **"Phone number starts with"**
5. Choose from available numbers
6. Click **Buy Now**
### Notes
* Available numbers depend on country and provider
* Pricing and renewal are shown before purchase
* Some countries may have limited availability
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## Connect Number to Bot
After purchasing, assign the number to an agent.
### How it works
* Incoming calls to the number → routed to the assigned agent
* The agent handles the conversation in real time
### Setup
* Open the phone number
* Select **Attached Agent**
* Save changes
> Only one agent handles incoming calls per number.
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## SMS Usage
SMS can be used for notifications and communication.
### Supported actions
* send SMS to users
### Requirements
* correct country configuration
* valid recipient number
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## Management
In **Phone Numbers**, you can:
* view all numbers
* check status and pricing
* see assigned agents
* manage renewals
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## Best Practices
* use dedicated numbers per use case (support, sales, etc.)
* assign clear ownership (one agent per number)
* test both call and SMS flows
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## Notes
* PSTN requires an active telephony provider
* pricing varies by country