nedbank lawyers threaten to take me for judgement, whereas i have been paying the as per arrangement

I have made an arrangement topay nedbank monthly as im unemployed at the moment. They sent me through to their lawyers to arrange payment, of which i did... this is my third month paying the lawyers as per arrangement, only to find the letter on thursday demanding that i make the whole payment within 10 days otherwise i will be going for judgement...i dont understand how this is so, because theres an arrangement in place and i have been paying. right now im unemploymed so how will i even manage to pay the whole amount let alone in 10 days. they treat us as if we dont know our rights as consumers...please could someone assist in this matter.