ask him why that balance job had to be done, if there is a good execute or reason whatever, escalate to his manager then to the manager of his manager, until you get your money back.
if the road isn't that bumpy, and you didn't change your TIRE(not rim) in the past 12 months, i dont see any reason to do the balancing.
if you had your TIRE changed/installed, then it's highly recommended to do the balancing.
if you just had the RIM/WHEEL installed, then it's not required either.
GET YOUR MONEY BACK!!!