Madison Hills University — Threatening phone call

I was a student from this Madison hills university and paid the amount of more than 6000 USD for certificate registration, various accreditation in 2014 now after three years yesterday again got the call from Ministry of higher education in Saudi Arabia and saying that your degree is not accredited regarding this need to pay again 4500 USD to get the Saudi council attestion.See Top 10 Worst Companies in California, MDSo now I have doubt whether this university is a real one or fake? And advise me how should I relive from this threatening call.
Senthil