Unfairly handing over clients!!!

I was offered early settlement which I took and paid my account and now I am being hounded for payment and handed over for the remaining balance which was confirmed as being written off. Seems as though this is a way of tricking clients to pay then hand them over for non-payment of the remaining balance effecting my credit rating unfairly.... As if people are not already struggling during this time of a pandemic now businesses thinks it is fine to further exploit and rip people off!!!!