JAS
TARLAN.

The product is a Flutter mobile app, a Kazakh / Russian / English website at jastarlan.kz, and a Laravel back-office where support agents work. The app surfaces four jobs — buy a new card, top up an existing card, check the balance, see the call detail — and a profile area that holds the user's cards, their purchase history, their top-up history, the offer agreement, and a delete-account flow that respects the data rules around this kind of clientele. The website mirrors the same flows for browsers, plus a public "check this card" form that doesn't require an account, so a relative without the app can confirm the balance the night before a call window opens.

The interesting part is what sits behind the four buttons. Each card is a SIP-side identity — its number is provisioned in a soft-switch that handles the actual call routing from the taxophone to the family destination, with per-minute deduction and the whitelist enforcement against the family's allowed numbers. Top-ups arrive over the Kaspi Pay integration: the user picks an amount, the app opens a Kaspi deeplink or a QR, the payment lands on a Kaspi webhook that we verify against the user's phone-bound profile and the card's MSISDN before crediting balance. The first-line conversation with the support team runs through a WhatsApp Business chatbot — payment confirmations, missed-call notifications, balance alerts — and any thread the bot can't close opens a Bitrix24 deal so a human can pick it up without losing the chat history.

Security is not optional in this category. The Laravel layer pins each profile to a single MSISDN with SMS-OTP, ties Kaspi receipts to the phone that paid, and signs every SIP-side credit with an HMAC so the soft-switch only accepts top-ups from the back-office it trusts. The whitelist of numbers a card is allowed to dial is set on the family side and enforced on the SIP side — the taxophone cannot reach a number the family hasn't approved. Suspicious patterns (top-ups from a phone that doesn't match the profile, sudden balance burns, calls outside the whitelist) flag the deal in Bitrix24 for an agent to call back manually. The point of the work was never the surface — it was making the surface small and trustworthy on top of a stack with a lot of moving parts.