Settlement gone wrong

I am at my wits end we had a business account with FNB things happen and the business closed. We were handed over to LGR attorneys they came back and said that they have a settlement offer for us in December, we paid and signed to say that we will no longer be able to have a business account at FNB it was fine when we went in to close the account we were told that there is still a portion of the overdraft we told the branch that we have a settlement letter and that we paid what they told us to pay. When I contacted LGR they said the amount will remain there for ever and a day and accrue interest which we will be liable for. It does not make sense FNB gave the offer account should now be closed! We were willing to pay the account fees for Dec and Jan because that is when we went in. Tried to contact LGR the lady is super rude. And kept on thretting me. Dobt know for what we dont owe anything on the account. Can someone from your team please contact so that i can get LGR to stop contacting me and sending sms stating something about S19? Which i dont understand!