Agreement broken

I sm unemployed now and have been medically boarded..I have a home loan n a personal loan with fnb..I've made means to pay my mond despite being unemployed..I made an agreement to psychology r250 towards my loan and stuck to my promise last month..to my surprise fnb lloans took 1800??? I never gave consent for that amount. How must I get mmy chronic medicmedication when there's no funds in my account. .please take the first 250 as agreed and bring back the difference. I will start paying this up to date as soon as I get my monies from tracker in 6 weeks time roughly.