A link like this belongs on the Turkish version of your website, in your Instagram profile, on the back of a printed catalogue or as a QR code on a trade-fair stand. When the buyer taps it and sends the greeting, they have started the conversation, which opens the 24-hour window: your team answers in free-form messages, each charged as a service reply.
Every Turkish letter outside plain ASCII, such as ş, ğ, ı, İ, ç, ö and ü, becomes six characters once encoded, so a short Turkish greeting makes a long link. Keep the prefilled line to one short sentence and test the link on a phone before it goes to print.
A first message from the buyer is also the clearest start in a country that attaches consent rules to commercial messages. Promotions you send later are a separate question; the Türkiye guide sets out Law 6563, KVKK and the open İYS question.