Most horrific customer service & business

I placed an order on 9 Dec for 7 books. On 18 Jan I received 3 of the 7 books ordered. I’ve mailed them 9 times since the 18th Jan & tried calling at least 20+ times with no answer!! I am fed up….. the service & communication is non existent. I don’t know how they can be in business. These are school textbooks that I ordered & my sone now doesn’t have books to work from! It’s totally unacceptable!