An unexpected phone bill usually has a simple cause: phones that can dial anything, at any time. An IP PBX lets you decide exactly who can call where, without taking phones away from staff. This guide explains call restrictions, often called class of service, and how to set them up sensibly.
What is class of service?
Class of service (COS) is a set of rules that decides which numbers each extension can dial. For example, reception may call local and mobile numbers, the accounts team may call national numbers, and only management may call international numbers.
How call restrictions work in Voxdial
| Layer | What it controls | Example |
|---|---|---|
| Global patterns | Number patterns the whole system recognises | +91% for Indian numbers, 00% for international |
| COS rules | Reusable templates of allowed patterns | Local only, National, International |
| User rules | Exceptions for one extension | The CFO can call international |
| Internal restrictions | Which extensions can call each other | Reception cannot call the directors’ extensions |
| Outbound routes | Which trunks calls use, when, and with what PIN | Block international after office hours; ask a PIN for STD |
A call goes through only if the extension’s class of service allows it and an outbound route matches it.
Practical restriction plans
Small office
- Common area and meeting room phones: internal and local only.
- Staff phones: local and mobile.
- Management: national and international.
Hospital or hotel
- Ward, room or guest-area phones: internal only, or internal plus emergency numbers.
- Nursing stations and front desk: local and mobile.
- Administration: national.
Call centre
- Agent phones: only the routes needed for their campaigns or callbacks.
- Supervisors: national.
Time-based restrictions
Outbound routes can be limited by time group, so international or long-distance calls are allowed only during office hours. Routes can also ask for a PIN, so expensive calls need authorisation.
Blocking unwanted callers
The blacklist blocks incoming calls from specific numbers instantly, and numbers can be imported in bulk from a spreadsheet, with a note on why each was blocked.
Internal call restrictions
Sometimes the issue is not cost but privacy: a public phone in the lobby should not ring the managing director directly. Internal call restrictions block chosen extensions from calling others, using exact numbers or patterns.
Reduce the bill further
- Move from PRI or analog lines to SIP trunks, which are usually cheaper per call.
- Connect branches on one PBX so calls between offices are free.
- Review the call statistics report for long outbound calls; Voxdial lists outbound calls longer than a set number of minutes.
Voxdial IP PBX by BitVoice includes class of service, internal restrictions, time-based routes, route PINs and a blacklist, managed from one web console. Talk to us.
FAQs
How do I stop staff from making international calls on office phones?
Give their extensions a class of service that allows only local or national numbers, and allow international calls only for extensions that need them.
Can calls be restricted by time of day?
Yes. Voxdial outbound routes can be limited to a time group, such as office hours, and can ask for a PIN.
Can I block calls from a specific number?
Yes. Add it to the blacklist; numbers can also be imported in bulk from a spreadsheet.
Can I stop one extension from calling another?
Yes. Internal call restrictions block chosen extensions, such as lobby phones, from calling others, such as management.
