FRUSTRATED & want to do the right THING

I bought a 2nd hand car @ Inspectacar in 2018. I had issues with dealership and well WB didn't really do much to assist. I was unemployed for a few months in 2020 and during that process communicated with WB. I eventually went into debt review. I have been faithfully paying since - arrears about 4 months or so. My period was increased - from 2023 to 2027 which means I have to pay for 9years ( 4months of arrears=extra 2/3years). I have queried this with my SP (DEBT REVIEW company) but that was not very fruitful. My interest rate is currently 15.50%. I requested settlement letter and my balance on my statement says 289k & settlement amount 300k - DOESNT MAKE SENSE. I need 2 issues escalated - 1. interest rate, 2. Settlement amount. As i want to sell my car nobody will/can pay this amount....I requested the same in Feb/March 22 and the settlement then was 319K - its like almost impossible to get out of this. I will lodge complaint with my SP & the OBS as well. I called WB & was also sent from pillar to post......