FNB Can't allow me to sell my house

I'm selling a house but FNB through Thabo Zwane at White River branch decided to hold on to registration documents unless I provide guarantees that the business credit card account I have with the bank is going to be settled. I never signed off the house as sercurity when taking the credit card. I find this extremely unfair. I regret taking many accounts with one bank because it seems this gives them the previlege to lay their hand on my little asset which is bonded with the same bank without following any proper processes.