Social Recruiting Strategies Conference , GSMI Web threatening to report to collections if I fail to pay the academic discount they offered San Diego California

I am an academician. I was interested in attending Social Reruiting Strategies Conference (#SRSC). I requested Global Strategic Management Institute (GSMI Web) for "May I confirm your registration?" 

I responded that I won't be able to attend. At this, they threatened me to pay $1000 or face being reported to collections. 

I find it outrageous. I did not register for the event. I only checked for the discount. I did not use the link they gave me to pay. There are still many days to the conference. 

It seems that they find it hard to fill conference. By using the threat of collections, they arm twist people to pay for it.