lewis Lewis Wil kill me

Good day, .I'm the customer at Lewis store, I open account in 2022 wth credit of 45k, recently checked my statement I'm still owing 48k with interest of 36k, 2 year back I went to store asking then to reduce instalment to 1.5k they agreed, this year February I asked them to increase the installment to initial agreement of 2.4k, to my surprise when I enquire about my balance still at 48k, they told me both head office and branch that I ve been paying interest....I'm.shck and feel like I've been playing, now I can't pay other things I'm owing, I'm stuck with Lewis, the branch only told me if I stick to initial agreement I'll be now owing 11 k, my concern all these year I've been paying who, what?