SAN FRANCISCO Bob Foremans architecture firm ran up a $166,000 phone bill in a single weekend last March. But neither Mr. Foreman nor anyone else at his seven-person company was in the office at the time. »finance.yahoo.com/news/p ··· 295.html
"The law is not much help, because no regulations require carriers to reimburse customers for fraud the way credit card companies must."
There's nothing in common re the hack between a phone system vs a credit/debit card so it shouldn't be any surprise their treated differently.
PBX etc... abuse is due to weak credentials which is within the complete control of the user where credit/debit card abuse is often completely out of the users control.