Welcome to the forum
I don't think you really need to book in advance if you aren't going to visit the museum during a temporary exhibition.
Nevertheless these are the contact info of the Accademia Museum in Florence:
phone: 0039 055 2388612
Fax: 0039 055 2388764
For info and bookings
Firenze Musei, phone: 055 294883
booking charge: € 3,00
Hope this helps, enjoy your visit.