This company is contacting regarding a private loan that's in default. They do not have a Certificate of Good Standing on file in my state. Should I refuse discuss the matter with them?
If you're concerned about private student loan collections, you should speak with a lawyer. Private student loan debt is handled much more similarly to car loans or mortgages - and each bank can use whatever collection agency they want.
GC services debt collection company trying to collect a debt from you?
GC Services is a student loan debt collector. You can read more about it here (https://thecollegeinvestor.com/20026/student-loan-debt-collectors/#tab-con-19).