Vertex Solution of no assistance

Hi, I'm very disappointed with Vertex. They offered me a 60% discount a few months ago, now when I have the cash to settle the amount they are now withdrawing their discount and requesting me to pay the full outstanding amount. They stated that the discount is not available any longer due to a tax campaign that they were running at that time. How do I move on from here as they are refusing to provide me with the discount that was promised to me.

Staff are so arrogant and unhelpful.

Please assist.