A Company "home From College" Is Threatening To Sue Us For $2500

We used their services to source freelance marketing candidates. The candidates were unqualified and we did not move forward with them. So, we decided to cancel our subscription. Now, the company is trying to charge us a $2,500 buyout fee which is bouncing from our account, alleging that we paid candidates by means other than their platform. Home From College is threatening to add 1.5% interest per month on the fee and to also pursue legal action unless we pay them.

To me, this seems like an unenforceable penalty clause.

here is the clause from the contract:

Subject to applicable law, you agree to use the Platform to make all payments for work directly to Students that have been accepted to a GIG you have listed on the Platform. In the event that you circumvent the Platform to pay any Student from the H\FC community for work performed, whether for such listed GIGs, or any other work, using a different method than the Platform, H\FC reserves the right, in its sole discretion, to charge you a $2,500 "buy-out" fee within thirty (30) calendar days of the date you connected with the Student through the Platform. For the avoidance of doubt, a $2,500 "buy-out" fee is due and payable on per Student that the Client makes any sort of off-platform payment to, whether the engagement between Student and Company relates to duties or responsibilities in a listed GIG or not. The buy-out fee is directly connected to the Student, not to the GIG description or tasks.

here is the link to the full contract:

https://homefromcollege.com/client-terms

What should we do?