Billing & debiting for items that were collected

We upgraded our PBX systems with IS. They took our old equipment when they delivered the new equipment on 12 February 2015. Internet Solutions (IS) have been charging us for the old equipment as well as the new equipment since. I queried this on 11 June 2015. This issue has still gone unresolved and we are still being debited for old and new items. We are a small company that cannot afford to pay this much for a phone system. Our account person is completely unhelpful and denies not knowing what happened at the start of this upgrade...I'm seeing red with frustration. It is almost October and now they're asking us for a cancellation of the equipment so that they don't charge us in future. I can't understand why they are oblivious to what was collected and in their inventory at present with the UPGRADE!?!?!?!?! I'm never going to use Internet Solutions and will certainly ensure that everyone knows how terrible they are - high staff turnaround (no surprise), POOR to NO customer service, no accountability and no respect for their clients. I'm sick with frustration and shock as to how poorly this is being handled. They are happily *****ing from us on a monthly basis.