FNB refusing to refund

I made a transfer to a residual account which is still subject to legal proceedings in error. I found the preson resposible for the account but after promises to call me, It just ended up in no repsonse from FNB. There is apparently no way to contact them but via email. What do I do if they dont respond via email anymore. They are not entitled to the funds transferred in error and I am requesting a refund.