> ## Documentation Index > Fetch the complete documentation index at: https://baas-api-docs.rexmfbank.com/llms.txt > Use this file to discover all available pages before exploring further. # Buy a data plan > Debits the partner Master account and buys a data plan. `amount` must match the selected plan (`tariffTypeId`). Requires an `Idempotency-Key` header. If the selected provider is down but an alternative is available, the API returns **HTTP 409 with `status: success`** and a `plans` list — not an error envelope. Show those plans and retry with a **new** idempotency key, because the body will have changed. ## OpenAPI ````yaml /openapi.yaml post /services/bills-payment/data openapi: 3.1.0 info: title: Rex Banking-as-a-Service API version: 1.0.0 summary: Embed real bank accounts, transfers, and collections into your product. description: | The Rex BaaS API lets you provision virtual bank accounts, move money between them, accept inbound transfers, collect at merchant terminals, and pay bills for your end customers — all under your own brand, backed by a real bank ledger. This reference covers every endpoint your integration will call. If you're just getting started, read **[Getting Started](/introduction)** and **[Authentication](/authentication)** first — most integration questions are answered there, not in the endpoint list. All endpoints are versioned under `/baas/api/v1` and return JSON. See **[Errors](/errors)** for the shared error envelope, and **[Sandbox vs. Live](/guides/sandbox-vs-live)** for how test and production credentials differ. contact: name: Rex BaaS Support email: baas-support@rexmfbank.com license: name: Proprietary — for approved Rex BaaS partners only servers: - url: https://api.rexmfbank.com/baas/api/v1 description: Rex BaaS API security: - BearerAuth: [] tags: - name: Authentication description: Register a partner account, verify it, log in, and manage credentials. - name: Onboarding description: | The one-time KYB (Know Your Business) flow every partner completes before going live — business details, a compliance representative, supporting documents, and signing the partner agreement. - name: Wallet description: >- Your business's own settlement balance — the account every virtual account nets into. - name: Virtual Accounts description: | The core product — dedicated bank account numbers you issue to your own end users, with full transfer and transaction capabilities. - name: Webhooks description: Configure where and how Rex notifies your system of events in real time. - name: Partner Settings description: >- Account security, team members, disputes, and document management for your own partner account. - name: Services description: | The catalog of optional products a partner can subscribe to. Virtual accounts are not in this list — they are available without a subscription. Bills payment is. - name: Bills Payment description: | Buy airtime, data, electricity, and cable TV for your end customers. Each purchase debits your own Master account. Requires a Bills Payment subscription — see **[Services](/guides/service-subscriptions)**. paths: /services/bills-payment/data: post: tags: - Bills Payment summary: Buy a data plan description: | Debits the partner Master account and buys a data plan. `amount` must match the selected plan (`tariffTypeId`). Requires an `Idempotency-Key` header. If the selected provider is down but an alternative is available, the API returns **HTTP 409 with `status: success`** and a `plans` list — not an error envelope. Show those plans and retry with a **new** idempotency key, because the body will have changed. parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: type: object required: - phone - amount - network - tariffTypeId properties: phone: type: string pattern: ^0\d{10}$ amount: type: number minimum: 50 maximum: 500000 description: Must match the selected plan. network: type: string maxLength: 15 description: '`mtn`, `glo`, `airtel`, or `9mobile`.' tariffTypeId: type: string description: Plan identifier from **Get data plans**. force_provider: type: string nullable: true description: Force a specific provider key. email: type: string format: email nullable: true customer_reference: type: string nullable: true maxLength: 100 example: phone: '08012345678' amount: 1500 network: mtn tariffTypeId: MTN_DATA_2GB email: customer@example.com customer_reference: customer-123 responses: '200': description: 'Purchased. `data` is a bills transaction with `bill_type: data`.' content: application/json: schema: allOf: - $ref: '#/components/schemas/SuccessEnvelope' - type: object properties: data: $ref: '#/components/schemas/BillsTransaction' '400': description: '`INSUFFICIENT_BALANCE`, or a missing `Idempotency-Key`' '403': description: '`NOT_SUBSCRIBED`' '409': description: | Either a conflict (`MASTER_NOT_PROVISIONED`, `DUPLICATE_REFERENCE`, idempotency still processing) **or** a provider fallback. The fallback is `status: success` with `failed_provider`, `next_provider`, and `plans` — retry that selection with a new idempotency key. content: application/json: example: status: success message: >- Your selected provider is temporarily unavailable. Please choose a plan from the alternative provider. data: failed_provider: provider-a next_provider: provider-b plans: [] '422': description: '`INVALID_PLAN_AMOUNT`, `DAILY_CAP_EXCEEDED`, or `VALIDATION_FAILED`' components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: true description: | Required on purchase endpoints. Use a new key for each intended purchase, and reuse that same key when retrying the same request after a timeout. A completed key replays the original response. The same key with a different body is rejected. Keys expire after 24 hours. A missing key returns `400` with no `error_code`. schema: type: string maxLength: 255 schemas: SuccessEnvelope: type: object properties: status: type: string enum: - success message: type: string data: description: Endpoint-specific payload — see each operation. BillsTransaction: type: object description: | A bills-payment debit against the partner Master account. `id` and every `*_id` are strings. Money fields are decimal strings. properties: id: type: string example: '101' company_id: type: string example: '28' master_savings_id: type: string example: '55' bill_type: type: string enum: - airtime - data - electricity - cable direction: type: string enum: - debit amount: type: string example: '1000.00' fee_amount: type: string example: '0.00' balance_after: type: string example: '49000.00' reference: type: string example: PROVIDER-REFERENCE status: type: string example: successful narration: type: string savings_transaction_id: type: string example: '9001' meta: type: object additionalProperties: true created_at: type: string format: date-time updated_at: type: string format: date-time securitySchemes: BearerAuth: type: http scheme: bearer bearerFormat: sk_live_... / sk_sandbox_... description: | See **[Authentication](/authentication)** for the full explanation of session tokens vs. API keys and when each is used. ````