Turbo Diesel Engine Parts sells marine and industrial engine parts to trade customers across Europe, and its customers were already on WhatsApp. We built what answers them now: a menu on the number they already use (Sales, Track an order, Admin), an assistant that captures the enquiry from a fixed facts sheet and hands it to a person rather than guessing, a reference number allocated from the client's own price sheet, and a console where the representatives answer. Every entry point — the site button, a link, a QR if one is ever printed — goes through one redirect on our own domain, so a number change never invalidates any of them. The 31 approved message templates live in git beside the code, held equal to the account by a test, with a rebuild command for the day Meta or Twilio has to be started again. 28 states, 127 transitions, 119 of them walked by a test; 426 customer journeys mapped.