Find the phone numbers of customers using the most common policy type among the available policies.
return customers ;return policy types of #1 ;return number of  #1 for each #2 ;return #2 where #3 is  the   highest ;return #1 where #2 is  #4 ;return phone numbers of #5
['select', 'project', 'group', 'comparative', 'comparative', 'project']