In many states a mediation or arbitration clauses are allowable in client engagement agreements. I am not sure whether this is the case in Tennessee. Now, as a general principle, while many states allow these dispute resolution clauses the specific terms may not be allowable.
You should speak with a local attorney regarding your issue. Contact people you know and trust for referrals. If you have no referrals, contact your local bar association for their referral program. Good luck.
DISCLAIMER—This answer is for informational purposes only and discusses general legal principles, trends, and considerations and is not intended as specific legal advice regarding your question. This answer does not establish an attorney client relationship. For legal advice, you should retain legal counsel in your state for advice regarding your specific circumstances.