I am trying create a rule that will fire if the field is not blank and the length of the field is 7 or 10 or if the field does not start with 609. Here is what I have. The problem I had was the rule was not firing as expected as a result of my logic.
LEFT(Phone__c, 3) <> "609",
LEN(Phone__c) <>7, LEN(Phone__c) <>10 ) )