Std Bank unable to update my email address with credit card department

For months I have spent excessive effort to try and achieve the simple task of changing my email address with Std Bank. This has involved visits to branches, phonecalls and countless emails. My address finally appears correct with most Std Bank departments (surely there should just be one central client database?), but I still receive my credit card statements to my old address after months of begging. My requests are now ignored, and I don't know what else to do. It's JUST AN EMAIL ADDRESS that I have changed in person at a branch - how hard can it be!?!