If the drafting attorney is not specifically named as a trustee or advisor in the trust, you have no obligation to consult him. You do, as a trustee, however, have obligations to act in good faith and in accordance with the trust instructions and overall intent. If the trustee has no written obligation to use a certain law office, then he or she should be able to consult a different attorney. You should of course, consult with an attorney of your choosing regarding how to proceed with management of the trust and its assets.
You should retain some other lawyer to represent you as trustee. The lawyer works for you not for the trustor or the heirs. The drafting lawyer has no right to charge the trust estate for any services you did not request. If he believes that he has a legal duty to speak to these folks, that's fine except the trust doesn't have to pay for it. Go find another lawyer.
DISCLAIMER: The response herein is not legal advice and does not create an attorney/client relationship or any right of confidentiality between you and the responding attorney. These responses are intended only to provide general information about perceived legal issues within the question. Each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer is not a substitute for competent legal advice from a licensed attorney that practices in the subject area in your jurisdiction and who is familiar with your specific facts and all of the circumstances.