---
title: "Detect a recent SIM swap or carrier port"
method: POST
path: "/v1/payg/sim-swap"
tags: ["x402 pay-per-call"]
---

# Detect a recent SIM swap or carrier port

`POST /v1/payg/sim-swap`

## Request

- Base URL: `https://api.relayshield.net`
- URL: `https://api.relayshield.net/v1/payg/sim-swap`
- Auth: none required

Check whether a phone number has had a SIM swap or carrier port in the last 24 hours via real-time carrier lookup. A recent swap is a strong signal of an active account-takeover attempt targeting SMS-based 2FA. Call before trusting an SMS OTP from this number.

**Billing.** $0.25 in USDC per call over x402, on Base or Solana. No API key, no signup and no
subscription. Send the request with no payment header, take the `402` challenge that comes back,
pay it, and repeat the request. Only successful calls are charged.

## Request body

- object
  - `phone` string, required: Phone number in E.164 format

## Response `200`

Payment settled and the check ran. `ok` is true and `data` holds the result.

- object
  - `ok` true, required
  - `data` object, required

## Other responses

- `400`: A required field is missing or malformed. Never billed.
- `402`: Payment required. The body carries a complete x402 version 2 challenge with the accepted networks, the amount in USDC base units, and the recipient. Pay it and repeat the request with the payment header.
- `405`: Wrong HTTP method. Every endpoint is POST.

---

[API](https://skmtc.dev/relayshield/apis/relayshield-api.md) · [All operations](https://skmtc.dev/relayshield/apis/relayshield-api/llms.txt) · [OpenAPI document](https://skmtc.dev/relayshield/apis/relayshield-api/revisions/4d4721b936dd?raw)