Mobile Recharge Reselling API Needed

I need a robust mobile-recharge reselling API that works seamlessly across all operators. The goal is to let my platform trigger prepaid top-ups for Airtel, Jio, Vi, BSNL and any other carrier without manual intervention, while keeping every transaction traceable in real time.

Core requirements
• Full coverage of every Indian mobile operator; future addition of DTH or data-card endpoints should remain possible, but the first milestone is prepaid mobile only.
• Auto-retry logic that attempts a failed recharge again within a configurable window and stops once the operator confirms success or a hard failure.
• Real-time reporting: webhook or polling endpoints that push back status updates, balance changes and failure reasons so I can display them instantly on my dashboard.

Deliverables
1. REST or JSON-RPC API specification with authentication flow.
2. Sandbox credentials for integration tests.
3. Sample code (PHP or Node preferred, but any language is fine).
4. Postman collection and a short setup guide.
5. Final hand-over after live recharge demos showing the auto-retry and real-time callbacks working for at least two operators.

Acceptance criteria
• A test recharge against each major operator completes successfully or fails gracefully and is retried automatically.
• The reporting endpoint pushes status within 5 seconds of operator response.
• Clear documentation lets a junior developer integrate in under one day.

Please clarify which tech stack you will use on your side and how you secure the API keys.