If you have access to the existing dashboard you should be able to unclaim the serial number from one organization and add it to another. This brings on some problems as well because to unclaim a device it has to be completely removed from any networks in the organization. After you unclaim it you should be able to claim it into you new organization and then add it to a network.
A better solution may to work with you support team and see if there are options for a company transition of the Organization that contains all of the devices.
You should ask the existing IT company to add a new administrator that you nominate (which could be yourself - there really should be someone in your company that has adnministrator rights if you own the kit).