Proof of Bond Substitution

Last week I had sent the below complaint to-date I haven't had any resolutions.

"One again I am have issues with Standard bank homeloans my query was closed without a clients resolution I am unhappy with the fact that you can't provide me with a proof of substition which is a legal obligation that I get some sort of proof that the account was substituted . Even after I had sent an escalation to the relevants departments "leaders" Simon Malan and Sarika Anandram on Friday I had still had no response ."