Lewis Store East London providing bad service to customers

I bought a restonic bedset in 2022 at Lewis East London 3-5 Gladstone Street 5201. Six months later the mattress got fault, the coil springs pop-out about 5 springs. I reported the issue to the Branch manager and to the stock controller Anex Lewis and nothing had been done till today. The mattress damages my sheets and duvets. What's confusing to me is that I'm still paying monthly installments to these people, but they don't show any conscious to assist me with this issue.