What customers receive
A customer who books gets a confirmation. After that, depending on what happens, they get a reminder, a message that the booking moved or was cancelled, and a no-show message. Email always goes out. Text messages go out when you have switched them on. They are off by default for a new business.
Email comes from your business's name, and a reply reaches the email address of your location. Every text ends with a link to stop texts, "Stop texts: link", shortened to "Stop: link" when the text would otherwise grow by a part. Where a country allows no links in a text, the text goes without it and the customer gets the way to stop by email instead. A customer who stopped reminders gets none.
Reminders
Reminders and the text switch are in Settings, not under Messages. On the web and in the app, open Settings, then Customers, then Reminders and SMS.
The first reminder goes out 24 hours before the appointment unless you change the hours. You can switch on a second reminder, "Second reminder, on the day". It is off by default, it goes 3 hours before the appointment, and it never goes before 08:00 on that day, so an appointment at 08:00 or earlier gets no second reminder. The first reminder has no 08:00 limit.
A service can have its own reminders, set in the Catalogue under Reminders. They replace the business default for that service, and like the second reminder they never go before 08:00 on the day. Text reminders still follow the text switch, "SMS messages", in Reminders and SMS.
Texts cost money, email does not
Each text message is charged to you, and none are included in any option. A monthly limit is set as a safety, and you can change it in Reminders and SMS. The amount per text is on the prices page. Email is unlimited and has no charge in every option.
Your own words
Open Messages, Message texts. You can edit every text, links included. If you remove the move or cancel link, ServeCounter shows a warning, and Restore ServeCounter's text puts the original back. The calendar file stays attached to every confirmation email whatever the text says.
A text can have up to 1,600 characters. The editor shows how many parts it will be and what it costs.
The "Booked with ServeCounter" line depends on your option. See The trial and choosing a plan.