Bad customer service

So I decided to call to file a complaint and yet I was told I cannot due to insufficient documents which I was never told about or contacted that they were needed , hence the point of filling my complaint. So it’s my right to complain but yet it depends on the complaint I want to file , am very confused onto how standard bank operate and treat their clients ! I’ve left a complaint before and trust me it helped with nothing cause even today the investigator has not contacted me on the matter not even an email , I was not even put through to the complaints department I was told to hold so they can talk to each other and conclude wether my complaint is valid or not !