A contract or installment account may provide for the payment of reasonable attorney's fees and actual court costs if it is referred to an attorney for collection. Reasonable attorney's fees and costs shall be awarded to the prevailing party in any action on a contract or installment account subject to the provisions of this chapter regardless of whether such action is instituted by the seller, holder, or buyer. Where the defendant alleges in an answer that the defendant tendered to the plaintiff the full amount to which the plaintiff was entitled, and thereupon deposits in court, for the plaintiff, the amount so tendered, and the allegation is found to be true, then the defendant is deemed to be a prevailing party within the meaning of this section.