Unfair Interest and Blacklisting Threat Due to Cartrack's Unresponsiveness

Last year, Cartrack offered me a discount on my outstanding balance, which I accepted and used to settle the account. However, the discount was never properly app****, leaving an inaccurate balance on my account. I responded to all of Cartrack's communications and followed up with their accounts department on several occasions to have the incorrect figure rectified. Despite my repeated efforts, they failed to revert to me or attend to the issue, and I received no feedback or resolution at any point. I remained willing and ready to settle the account, but could not do so because Cartrack had not supp**** me with the correct outstanding amount. After approximately three months of inaction on their side, they finally provided a figure — now with interest added to it — and have threatened to blacklist me. My dispute is not with settling the account. I have always been willing to pay. The challenge is the interest that has been added to the balance, which was caused in part by Cartrack's own failure to respond timeously and provide me with an accurate figure. I should not be penalised with additional interest for a delay that was not of my making.