What is theft of sale and is it considered a misdemeanor or a felony?

It is neither a misdemeanor or a felony. It is a civil matter. I think what your friend has here is a third party collector on him. I say this because of the eight years you mention. The debt is so old that they sell a list of outstanding debts to a third party who pays them and then tries to collect the debt. Tell your friend that the next time they call, to ask for contact information for them. Then send them a letter of cease and desist . After that, just ignore them.