Confirmation SMS and emails, as well as reminder messages, are considered ‘transactional’ messages, rather than marketing. It is part of the service your client asks of you, so you have a legitimate interest, and it is also in the client’s interest to get these messages. However, should a client come in and ask you to stop sending these messages, you should remove their consent to receiving reminder messages. Asking for reviews is also considered a transactional message, as it is part of your service.
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