If there was a contract in place for you to be charged 9.99% interest, that contract is enforceable--you may not be charged more than that. Even if the contractor could not find interest that low, it can only charge you 9.99% and will have to make up the difference out of its own pocket.Or even if the contract did not specific the rate, if the contractor represented, or promised, to you that you would pay 9.99% interest and that representation was a significant factor in you hiring them, you may be able to hold them to that promise under the theory of "promissory estoppel."Only if there was some clear disclosure (prior to you agreeing to have them do the work) that financing was subject to availability or change and you--in full knowledge of that possibility--went ahead with the work, would they seem to have a basis for charging you more. Otherwise, they will be held to what they contractually agreed to and/or to what they represented to you to induce you to do business with them. If necessary, you can take legal action (sue them) to force them to honor their obligation.