SELECT Accreditation_level FROM phone GROUP BY Accreditation_level HAVING count(*)  >  3
Find the accreditation level that more than 3 phones use.
[Schema (values) (types)]: | phone_1 |  chip_model : model_name (text) , launch_year (text) , ram_mib (number) , rom_mib (number) , slots (number) , wifi (text) , bluetooth (text) | screen_mode : graphics_mode (text) , char_cells (text) , pixels (number) , hardware_colours (number) , used_kb (number) , map (text) , type (text) | phone : company_name (text) , hardware_model_name (text) , accreditation_type (number) , accreditation_level (number) , date (number) , chip_model (text) , screen_mode (text);