An offer with a deadline
“Hi {{1}}, our festive sweet boxes are open for booking till 28 Oct. Reply BOOK and we will confirm your order. Reply STOP to opt out.” It names the customer, says what and by when, and asks for one action.
A reminder
“Hi {{1}}, a reminder that your order {{2}} is ready for pickup today until 8 pm.” Reminders about something the customer already did are utility messages, so keep them free of promotion.
A thank-you
“Thank you for shopping with us, {{1}}. If anything is not right, reply here and we will help.” It builds goodwill and invites replies, which keep the chat open for free-form answers.
Timing and frequency
Send in daytime hours, once or twice in a campaign, and not every day. Too many messages is what makes people block you, and blocks reduce your sending limit.