Annoyed customer

In 2021 I ordered an instant boiler and braai stand, I owed them like 7000, never missed a monthly premium but they keep on sending me a statement with the amount of 5000 that they say I'm owing, tried sending emails no reply, called the person who assisted me Xoliswa, she told me she's no longer working there,it's my first time having this bad experience and totally annoyed. And I'm not the only one even my colleague complains about this