A point-of-sale terminal that depends on Wi-Fi for its internet connection has a single point of failure. When the router, the ISP or the venue’s network goes down, the terminal can still read cards but cannot authorize anything — and every minute offline is lost revenue. The usual fix is a second, independent connection. A pre-activated data-only SIM gives the terminal its own cellular link on the AT&T, T-Mobile or Verizon networks, so payments keep going when Wi-Fi drops.
This guide covers what has to be true before a SIM will work in a POS terminal, the exact APN settings you need, and how much data a terminal actually uses.
Before you buy: three things to check
| Check | Why it matters |
|---|---|
| 1. The terminal has a physical SIM slot | Cellular failover needs a card slot. RelaxedSIM ships a 3-in-1 card (Standard, Micro and Nano), so one card fits whichever slot your terminal has. |
| 2. The terminal is carrier-unlocked | A carrier-locked device will reject a SIM from another provider. Check with your vendor or in the device settings. |
| 3. You can set the APN manually | This is the requirement that catches most people out. If the terminal’s software hides or removes the APN menu, you cannot point it at a new provider — check this before you buy anything. |
Clover Flex 4 and managed POS terminals
A merchant has reported using a RelaxedSIM data card in a Clover Flex 4 credit-card terminal setup. Managed devices need extra checks because the SIM slot, APN screen or cellular service may be controlled by the Clover reseller. Read our Clover Flex 4 data SIM and APN guide before changing the device.
Can you set the APN on your terminal?
On an Android-based POS terminal the setting normally lives here:
Settings → Network & internet → Mobile network → Access Point Names
Some vendors use slightly different paths (Settings → Connections → Mobile networks on many Samsung-derived builds). If you can reach an Access Point Names screen and add a new profile, the terminal supports manual APN configuration and any compatible data SIM will work.
If the menu is missing, ask your terminal vendor one question: “Does this build allow a custom APN for a third-party SIM?” Some locked-down POS builds only accept the operator profile baked in by the vendor, and a few are sold carrier-locked. In those cases no third-party SIM — ours or anyone else’s — will work, and it is better to find that out before purchase.
APN settings for POS terminals
| Setting | Value |
|---|---|
| APN | globaldata |
| Username | Leave blank |
| Password | Leave blank |
To apply them on an Android terminal:
- Insert the RelaxedSIM card and power the terminal on.
- Open Settings → Network & internet → Mobile network → Access Point Names.
- Tap + (or Add) and create a new profile: name it
RelaxedSIM, enterglobaldataas the APN, and leave username and password empty. - Save the profile, then select it in the APN list.
- Turn on Mobile data (and Data roaming if the option exists).
The same values work regardless of which of the three US networks the terminal picks up. Full details for every device type are on our APN settings page.
How failover between Wi-Fi and cellular works
The SIM provides the cellular link; how the terminal uses it depends on the device and the POS software:
- Automatic failover — most modern Android terminals keep Wi-Fi as the preferred network and fall back to mobile data when Wi-Fi disappears. This is the ideal setup for a backup link.
- Manual switching — some builds require you to turn Wi-Fi off (or mobile data on) to change the route. Staff can do this in seconds if you document it.
- App-level binding — a few POS applications bind to a specific network interface and will not follow the failover automatically. Check with your POS provider whether the app tolerates a network change mid-shift.
Whatever the terminal does by default, test it once: disconnect the Wi-Fi router, run a test transaction, and confirm the terminal authorizes over cellular. A backup link you have never tested is not a backup.
How much data does a POS terminal use?
Card authorizations are tiny — a few kilobytes each. Even a busy terminal typically stays well under 1GB per month unless it also receives software updates or runs a lot of cloud reporting over the cellular link. For a pure failover link that only carries transactions during outages, consumption is far lower.
That makes the larger pre-paid plans a good fit for this use case: a 24GB / 360-day SIM covers a whole year of backup connectivity with no monthly contract, and the 3GB / 30-day plan is a cheap way to test the setup first. Every SIM also includes a free 100MB / 7-day trial that starts on first connection, which is enough to validate coverage and routing in your venue.
Things that can trip you up
- Data-only means no calls or SMS. RelaxedSIM SIMs carry data only. If your POS provider sends activation codes by SMS, or the terminal needs a phone number, this type of SIM is not a fit.
- Carrier-locked terminals. Locked devices reject third-party SIMs regardless of the APN.
- Missing APN menu. See the section above — this is the hard blocker.
- Signal inside the venue. Basements, walk-in coolers and metal shelving weaken cellular reception. Test at the actual terminal location, not in the car park.
- Payment security is unchanged. The SIM only supplies the internet link; your terminal’s encryption and your provider’s requirements still apply exactly as they do over Wi-Fi.
Frequently Asked Questions
Will a data-only SIM work in a POS terminal?
Yes, provided the terminal has a physical SIM slot, is carrier-unlocked, and lets you create a custom APN profile. The SIM is pre-activated, so the terminal connects the first time it registers on the network — no activation call or portal.
How much data does a POS terminal use per month?
Card authorizations are a few kilobytes each. A terminal used only for payments normally stays well under 1GB per month, and a failover-only link uses far less because it carries traffic only during outages.
Will my terminal switch to cellular automatically when Wi-Fi goes down?
Most Android-based terminals do, because they keep Wi-Fi preferred and fall back to mobile data. Some builds need Wi-Fi turned off manually, and a few POS apps bind to one network interface. Test the failover once with a real transaction before you rely on it.
What if my POS terminal has no APN settings menu?
Then it cannot be pointed at a third-party SIM. Ask your terminal vendor whether the build supports a custom APN; if it does not, the device is limited to the operator profile it shipped with.
Do I need a static IP or a fixed APN for card payments?
No. Standard card authorization uses outbound HTTPS from the terminal to the payment provider, which works over the same globaldata APN as any other data connection. If your provider requires a VPN or a fixed IP, that is configured in the terminal or on the provider side, not in the SIM.
Can I move the SIM to another device later?
Yes. The SIM is not tied to a device — move it to any other unlocked device with a SIM slot and set the same APN there. See our activation guide for the general steps.