Can we sue the accountant in small claims or whatever courts appropriate for malpractice?

I am writing this query on behalf of my friend who was a legal resident alien between the years 2007-2010. He received an audit from IRS for his tax filings for the year 2008 and 2009 totaling around $5000 with interest. I consulted an accountant on behalf of my friend and was told by the accountant that an appeal can be made to reduce this outstanding with IRS. When asked how much could be saved, he gave us a number of 70% minimal waiver and charged us $1500 for making the appeal against 2008 and 2009 tax returns. The accountant charged about 30% of the fee based on the 70% waiver he promised. Recently, we heard back from IRS that the appeal by the accountant does not entitle my friend for a reduced tax and so he still owes the same money to IRS. When we got back to the accountant, he says nothing can be done and that my friend has to pay the money that IRS claims. At this juncture, the appeal made by CPA's original claim of 70% has been quashed by IRS and no relief of tax is provided to my friend. We asked the accountant to deduct a reasonable fee from the $1500 and repay back the rest of fee paid to the accountant as his fee was totally based on the 70% promised waiver from IRS. Since then the accountant has not at all been responsive to us. After a week of relentless pursuant to reach the accountant over phone and emails, he now says he is unwilling to refund any part of the fee. We feel that as the accountant knew my friend was not a resident in the country, he made a scapegoat out of him without even standing a chance to prove anything to IRS but still went ahead and represented him with a big failed effort. Now he is unwilling to give us any reasonable fee back as the fee itself amounts to about 30% of IRS outstanding amount. We want to claim what is rightfully ours and pay back IRS.