FNB withhold my funds without a reason and way forward.

I recently moved from Netbank to FNB and I have never regretted moving banks like I do now. FNB blocks my account with no communication before or after the block. I had to go to a branch and even when I went there, the team was unable to assist me. The bank blocked my account, then they withhold funds in my account saying it was instructed by sars. When I asked why sars is instructing them to do that, they tell me sars wont share with them because its confidential. So anyone can call and says fnb must hold someone's funds and they will, no questions asked? I sent fnb my statement of accounts to show fnb that the amount from sars is exactly what sars is meant to refund me, but fnb does not seem to care about that. Fnb instructed me to call sars, which I did and sars says there are not aware of such an instruction as it was not communicated from their system and never communicated from me. They are telling me that according to their system I already have my funds and sars does not owe me anything any more. I have been going to the Makhado branch since last week Friday with no help. My account is moving at a negative with no assistance from fnb to resolve the matter. The inconvenience and lack of problem solving from fnb has left me on a dead end with no idea where I need to go. There is nothing fnb is requesting from me to show as prove that the amount sars paid to my account is what was meant to be paid. All they keep telling me is that sars disputed the funds, but sars did not say on what basis is sars disputing the funds. FNB just decided to hold my funds and left me out inconvenienced. The funds were released to my account on the 26th August, but somehow sars disputed the funds on the 29th without a reason why, according to fnb consultants. All they provided me is some letter saying is from sars without a reason on why sars is saying my funds should be withheld other than that the funds were improperly deposited. When I supply the statement of account showing that the amount is correct, they dont seem interested. What other prove can I give outside of the statement of accounts provided by sars? If that is not the document they are looking for then why are they not specifying what documents they are looking for? FNB made it very difficult for me to trust them going forward.