We highly recommend using SMS for your marketing, to send your market appraisals and more. The only place SMS is required to be sent is in the Contracts - for two factor authentication.
If you do not wish to send an SMS with an appointment or market appraisal, click Edit and Send rather than Quick Send. Then only click send on the email tab.
If you do not wish to send SMS automatically for your portal enquiries or instant valuation enquiries, please visit Marketing and Autopilot>>Automations to turn these off.
Throughout the rest of Lifesycle, you need to manually click to send an SMS.