Applied Merchant System, Inc. Capital Payments Refuses to process transaction, then charges you for it. Chicago, Illinois

We used Applied Merchant Systems, Inc. to process normal daily credit card receipts with the exception of one transaction...we sold a piece of equipment.  AMS withheld the funds requesting a copy of the signed receipt to be sent to them via email or fax.  We were given a second option of reversing the charge.  We sent in the signed receipt.  AMS decided that they still would not release the funds to us; that our only option was to reverse the credit card transaction, so we did.  The merchant statement showed up and they charged us for the credit card processing fee.  We called to get them to reverse this charge and not to charge for reversing the credit card transaction.  They refused saying that we were not allowed to sell equipment.  We sold other things beside services, so not aware of this.  I asked to talk to a manager.  I was informed that that would not be possible.  I insisted and was put on hold for over 40 minutes with no one coming back on the line, I hung up.  I guess my next move is to hire an attorney.  Please save yourself the headache and get a different company.