More than likely, and hopefully as they see that contract out you can use your clearinghouse but you can't use both. You can only have one submitter ID. Should be ok though as long as your contract has a start date and they will deal with the contract for the other billing company. For example, your start date might be 4/1 and perhaps their contract ends 3/30. When you give the client your enrollment forms to fill out that should prompt them to be sure it's disconnected on the other end.