There are 2 complementary ways to get an appointment reminder from your Simple CRM calendar.
1) Once you have sent a quote, move the interaction (i.e. change the date and time of the interaction) to the date and time you want to call your customer back.
In this way, the tasks and appointments of the day are listed in the module Simple Office CRM (menu top -> Simple Office CRM).
2) You can complete point 1) by displaying your agenda on your smartphone or tablet. Each appointment (call back the contact in your case) will ring your mobile or tablet 15 minutes before the time of the appointment.
To view your calendar on an iPhone / iPad:
On a smartphone or Android tablet: