Register your phone number/account online first, then call them to pre book an appt
No need to call in on the day of appt. Only reason to call is to cancel but ideally you should do that a bit earlier
Watch the schedule on the day of your appt before coming in to make sure the girl showed up. From my experience they usually only text you if the girl is running late or suddenly left in the middle of her shift and they have to cancel your appt. If the girl no showed then they won't be guaranteed to text everyone, and will put some onus on you to check the schedule. That especially tends to be the case for girls with more problematic attendance