Picture a $500 order that comes in with a Google Voice number and a shipping address two states away from the billing address. On its own, none of that is proof of anything. Together, it’s the kind of pattern that can end in a chargeback weeks later, after you’ve already shipped. Phone validation is one of the cheaper signals you can add to catch that order before it leaves the warehouse.
Not every chargeback is stolen-card fraud; some are friendly fraud, where the real cardholder disputes a charge they actually made. Validating the phone number on an order won’t catch all of it. It gives you one more piece of evidence to weigh before you fulfill, and it’s evidence you can pull in real time at checkout.
What phone data tells you about a risky order
Fraudulent orders tend to carry small inconsistencies, and several of them show up in the phone number:
- A VoIP number on a high-value order. Disposable VoIP lines are how fraudsters stay untraceable, so a large order behind a Google Voice number with a mismatched shipping address is worth a closer look.
- A recently deactivated number. If the line is dead, the contact details may be stolen or invented.
- A geographic mismatch. The area code, or the location of the customer’s IP address, points to a different state or country than the billing or shipping address.
- A landline where you expected a mobile. If a customer says they got your SMS confirmation but the number is a landline, that story doesn’t hold together.
Treat these as inputs, not verdicts. Any one of them has innocent explanations. Stacked with the rest of your order data, they sharpen the risk decision.
Working it into your order flow
At checkout
Validate the number as the customer types it. The CheckThatPhone API returns line type, deliverability, and carrier in real time; pass the customer’s IP in the same call and you get its location too. If the number is invalid or looks high-risk, ask the customer to re-enter it or route the order to manual review before it’s confirmed.
In your fraud scoring
Phone results are most useful as features in the model you already run, not as a standalone gate. Reasonable rules to start from:
- VoIP number (carrier sub-type
IPES) plus a new account plus a high order value means elevated risk - A recently deactivated number plus express shipping means flag for review
- An IP location that doesn’t match the billing address means require extra verification
The same signals work at account signup, before there’s an order at all; see phone validation for onboarding fraud prevention.
After the order, for the borderline cases
For anything flagged, send an SMS code to the validated number before you ship. If they can enter it, they control the number they gave you, and you’ve added a real identity check on exactly the orders that warranted one.
How this cuts chargebacks
A chargeback starts when a cardholder disputes a transaction. Phone validation chips away at the rate in three ways:
- Blocking a fraudulent order before fulfillment means the chargeback never happens at all
- SMS verification leaves a record that the customer confirmed the order, which helps if you have to fight a dispute
- Cleaner contact data means fewer legitimate disputes from wrong addresses or unreachable customers
If you sell in a high-risk category like supplements, electronics, or subscription boxes, you already know every point shaved off your chargeback rate lands straight on the bottom line.
What the API gives you
For e-commerce fraud work, CheckThatPhone returns:
- Line type (mobile, VoIP, landline)
- Carrier name and subtype
- Deliverability status
- Recent deactivation (last 45 days) and current porting status
- GeoIP location and timezone
The complete API response format has the integration details.
Where to start
The fastest payoff is validating at checkout and feeding line type and GeoIP into whatever fraud scoring you already run. You don’t need a perfect model on day one; even a couple of simple rules around VoIP and geographic mismatch will catch orders you’re currently shipping blind. For more of the signals worth scoring, see vetting inbound leads: the phone signals that flag obvious fraud. The API documentation covers the integration, and the pricing plans let you start at your volume.