Enterprise License, switching plans

Need helps, please.

As a company we have changed to Enterprise license and accidentally, our division:6 accounts are changed from design standard (which we have been using years) to Video production plan. We have been asking a sales to switch the plan back when we realized the mistake and adding one more (to make a total of 7), and if there is any money loss due to the plan change, we may compensate those if adding one account will not cover.

However, despite the fact that none is written in the contract, the sales only repeat that the license is only able us to add but not change, which cost us more than double for 3 years, and no cancellation allowed. In total, we are paying more than a person simply bought any plan. The sales person says there is  a volume discount for enterprise license so we aren't "losing", and if that is the case, then we have asked what kind of discount we are getting which override the double payments, and no answers.  They insist verbal or face to face communication only, and as a product service or selling a license which we refuse as no record to be kept, I am pretty tiered talking with them over months and our work has been inefficient for not being able to use right plan.

Can we do anything to improve the situation,  and change the sales person please?? I think they are just on purposely wasting our time by not answering to lose the timing and opportunity to switch.  Your kind assistance will be so much appreciated. Thanks a million.