Very bad service

As a private client, I have noticed the deterioration in service. I received an email from the FNB suite informing me that there was documentation that I filled in incorrectly. When I queried what this was about, I was given no explanation and sent an email that the query was closed. I then called the FNB suite to find out what this was about and was still not offered an explanation, but told that someone would get back to me (spoke to someone named Mpho). No one got back to me and the following day I called back again to find out what this was about, and call was taken by someone else, who also has not resolved my query and has said someone will get back to me. Two days after this email was sent by my bank notifying me that there are supposed documents completed by me (which I did not do), no one has gotten back to me to explain what this is and why this query was opened and then closed without any explanation being offered to me. My question is, if I didn't fill in the documentation, who did? And why is FNB refusing to answer me on this? At this point the service has deteriorated to the point where I feel there is no other option but to change banks. Mind you, I am a private client having to chase after them. Even after all of these phone calls, no one has gotten back to me.