Check each account if it has unique numbers on mobile settings... some pva maker use same number in various accounts especially the indian numbers... if there is same numbers in the facebooks that you had purchased it is so likely that some of may looked pva but they aren't... once a number has been used again the old account where it was used is no longer a pva...
in NON PVA ACCOUNTS you cannoy set username
go to account settings , under username option.. if it is non pva it will ask for mobile number verification
You could go directly to this link to check : facebook.com/confirmphone.php