money has been returned to me buy Land of leather want all those extra charges and stuff as i missed a payment whcih is 628.00 more than i borrowed

i used the wrogn details

we bought a sofa from land of leather in dec 2005, on a one year free credit, my brother joined uni in september and went part time in his job and in dec he lost his job, so ohe asked me to pay the sofa which was £826, i made a online bank transfer from my account, but money went into a wrong account, and NOW the want £1486 to settle the account ( well that was 2 days ago, GOD ONLY knows wat it is today as interest is being added daily, My brother;s credit rating is going down he has always had superb credit score SOMEONE PLEASE HELP