Format Phone Numbers In SQL Server
Assuming that the [PhoneField] is 10 digits, such as '1234567890' then you could use STUFF to put the proper values in.  E.g.

select STUFF(STUFF('1234567890',7,0,'-'),4,0,'-');


But please note that this only answers formatting a phone number for the 10-digit answers.  If you are using internationally dialed numbers, you need to investigate the various forms of phone numbers you might need to handle.

See: https://en.wikipedia.org/wiki/National_conventions_for_writing_telephone_numbers