College SA supplies text books with mistakes

I enrolled with college SA for an N2 Electrical course, they supp**** me a N2 Engineering Science text book with mistakes in them, ranging from omitted symbols to incorrect answers for examples. They give you a 30 day money back guarantee, i only received the text book more than 3 weeks after enrollment, I gave them a week to try sort it out. But they were ignoring my emails so i canceled. Now they only want to give me a 40% refund which i think is disgusting.