Frozen Funds for selling a car

Sold my Car today , "To webuycars" which Im very sure FNB are fami**** with since they use FNB for their purchases . My funds were Put on Hold about a hour later, after the agents left with the car and all the documents . then FNB tells me I have to provide them with the Documents "which I dont have any more, thats how a sale works" otherwise they keeping my funds on Hold Indefinitely. What kind of Sceme are they running here when they are targeting people when they know very well the funds come from Webuycars. this is just harassment in my opinion, Il be closing my FNB accounts, sell off my shares I have with them and move to another bank.