Three Different Things, Often Used Interchangeably
When people ask "how can I receive calls from my home country without roaming?", they get pointed at three technologies that sound similar but are not:
- Carrier call forwarding — a feature of the SIM card and home network you already have
- Virtual phone numbers — separate phone numbers that exist on a provider's infrastructure, not tied to a SIM
- VoIP receiving — taking the call through internet protocols on a software endpoint instead of a phone
This article walks through each, what the call path actually looks like, what it costs, and where each one breaks. By the end you'll know which combination is right for your situation.
1. Carrier Call Forwarding
This is the original solution and the one most people try first because it requires no new accounts.
How it works
You set a forwarding rule on your home SIM through your carrier — either via the dial codes (`*21*+44...#` for unconditional, `*61*+44...#` for "no answer" forwarding, etc.) or in the carrier's app or web portal. From that point on, calls to your number either ring on your physical SIM first and then forward, or forward immediately, depending on the rule type.
What the call path looks like
```
Caller's phone
→ caller's carrier
→ your home carrier
→ home carrier rings your SIM (you abroad, doesn't pick up, or rule is unconditional)
→ home carrier dials the forward-to number on your behalf
→ terminating carrier
→ your destination phone
```
There are two billable legs: the caller's leg (paid by the caller, usually included in their plan to a domestic number) and the forwarding leg from your home carrier outward — usually paid by you.
What it costs
Most UK and EU pay-monthly contracts include domestic-destination forwarding in the monthly minutes. Forwarding to an international number (the common case when you're abroad) is typically charged at the carrier's international rate — £0.10–£1.50/min in most plans. This is the trap. Forwarding to your foreign mobile via the home carrier essentially turns every incoming call into an outgoing international call paid by you.
The few clean cases:
- Your home carrier explicitly bundles "forwarding included to any number" — uncommon but exists
- You forward to a virtual number that's effectively a domestic destination from the home carrier's perspective (more on this below) — then the forwarding leg is cheap or free
Where it breaks
Call forwarding is opaque. There's no log of forwarded calls in most carrier apps, the call goes through whether you wanted it or not, and you'll usually only find out you've been billed when the next bill arrives. It also has variable behaviour during travel: some carriers disable forwarding when the SIM is on a roaming network.
2. Virtual Phone Numbers
A virtual number is a phone number that lives on a provider's switch rather than on a SIM card. You buy or rent it from a provider, and you define what happens when someone dials it.
How it works
The provider operates a switch — historically a SIP server, in modern stacks often a cloud-native VoIP stack. The number is registered on that switch in the destination country's numbering plan, so it looks and behaves like any normal local number to anyone dialling it. When a call comes in, the switch consults rules you've configured and routes the call onward.
What the call path looks like for an inbound call to the virtual number
```
Caller's phone
→ caller's carrier
→ provider's local presence in the home country
→ provider's switch applies your routing rule
→ either: terminated to the provider's app (web app or mobile app) over WebRTC/SIP
or: forwarded to a normal phone number anywhere in the world
```
The provider holds the number and acts as the destination from the home country's network perspective. The original caller pays as if they made a local call — nothing changes for them.
What it costs
Two cost components on a virtual number:
- Monthly rental for the number itself — varies by country. The provider pays the local carrier for hosting it.
- Per-minute for whatever the routing rule does:
- If you receive the call in the provider's web app or mobile app: usually free (just data on your side).
- If you forward to a normal phone number: priced at the provider's standard outbound per-minute rate to that destination. With Voxa specifically, this is the same rate as if you were making an outbound call there yourself — e.g. €0.02/min to UK landline, €0.05/min to UK mobile, €0.04/min to Germany landline, €0.02/min to US.
Where it breaks
Virtual numbers are excellent at voice. They are weaker on:
- Inbound SMS — some providers support inbound SMS to virtual numbers, others don't. Many banks send 2FA only by SMS to specific local mobile prefixes, which a virtual number may or may not be on. Verify before relying on the number for 2FA.
- Emergency services — you cannot dial 999/112/911 from a virtual number and expect emergency services to find you. The number isn't tied to a location.
For 95% of inbound voice use cases, however, this is the cleanest solution available.
3. VoIP Receiving (The Web App or Softphone)
VoIP receiving is the layer underneath the virtual number — it's how you actually answer the call once it's been routed to your software endpoint.
How it works
When a call is routed to a software endpoint (a web app, mobile app, or SIP softphone), the provider's media server establishes a WebRTC or SIP+SRTP session to your device. The audio is captured by your device's microphone and speaker, encrypted in transit, and bridged to the originating PSTN leg.
What it costs
Receiving in a software endpoint typically costs nothing per-minute — it's just data, around 0.5 MB/minute. The monthly cost is whatever number rental you've paid for, plus whatever your data plan charges (essentially nothing).
Where it breaks
VoIP receiving needs an internet connection to work. If you're on a flight with no Wi-Fi, in a basement with no signal, or in a country that restricts VoIP, you cannot receive the call in the web app. In those cases the provider's failover rule kicks in — usually forwarding to a regular phone number you've configured as a backup.
Picking the Right Combination
For most people abroad, the optimal setup is a virtual home-country number with VoIP receiving in the web app, and conditional forwarding to a local SIM as a backup. That stacks the three technologies in the right order:
- The virtual number gives you a stable home-country address everyone in your life can dial
- VoIP receiving handles the call cheaply when you have internet
- Conditional forwarding to your local SIM catches anything you'd otherwise miss
For short trips (a week or two), carrier call forwarding alone can be enough — provided your carrier's forwarding rates to your destination country are reasonable, and you've checked that forwarding stays active on roaming.
For business use cases where SMS 2FA matters, you may need an additional service that specifically provides inbound SMS to a domestic-mobile-prefix number, or you may need to migrate the 2FA method (most banks now support voice 2FA over a regular phone call, which a virtual number handles fine).
Cost Summary
Comparable cost for 60 minutes of inbound calls per month while abroad:
- Carrier forwarding (foreign destination): £6 to £90, depending on plan and forward destination
- Virtual number with browser receive: monthly number rental only — typically €1–€5 — plus €0 per minute
- Virtual number with forwarding to local SIM: monthly rental + 60 × outbound rate to destination (e.g. €1.20 if forwarding to Spain mobile at €0.02/min)
- Wi-Fi calling on home SIM: usually €0 when on Wi-Fi, but doesn't cover the moments when you're not
The technical differences map directly to the cost differences. Once you understand the call path, the right answer for your specific situation usually becomes obvious.