who is at a breach of contract?

What is the name of your state? Florida
I am a small business owner that does IT support and I had a 1 year contract signed by a mid size business who just got a new president and he with held payment for 4 months for our service. We notified him we would stop supporting him a month ago if payment was not received in full. Now he is threatening with suing us for breach of contract because he had to go out and get someone else to fix their issues and wants to pass the bill on to us? Is this right? In the contract there is a paragraph stating that we at our sole discretion have the right to cancel accounts for non-payment.
Can he come after us for his down time even though we did warn them?
Help?

Unless you can post here the exact wording of this section of the contract how do you expect a valid answer?

thank you for your fast reply.
the exact wording in our contract:
We reserve the right to cancel accounts for non-payment in our sole discrection.

thank you for any insight

Then file a small claims action for the unpaid invoices against the company and let the judge figure it out.