Seller doesn't want to exit the business after the sale

Two months ago I purchased a graphic design business with an asset purchase agreement. The primary asset in this transaction is the client list. The previous owners agreed to transition these client accounts to me. The agreement has no provisions for the owner doing contract work after the sale for me nor does it stipulate any compensation for referred clients that were NOT listed as part of the purchase. The sellers are not exiting the business as agreed to nor are they willing to discuss a transition timeline. They remain in direct contact with the clients, are quoting the clients projects and tasks and doing the work. They are then in turn sending me a bill for the work which also includes the earn out percentage. They are not allowing me to manage the client relationships or quote the client to ensure that jobs are profitable. I suspect because the majority of the valuation is an earnout, they feel that client loss may occur if they step out too soon. This is a very real concern because I am suspecting that the sellers WERE the business more than they disclosed. Never the less, I feel as is this a breach of our agreement and so far my efforts to work this out has not been successful. I wish to know if my assumptions are correct from a legal standpoint and what my options are. Has anyone been in a similar situation and/or able to offer some advice?