Bad service

I opened an Easy Account in October 2018. Never before did I have any accounts with FNB, yet, they called me Miss Pretorius on the phone. Which means they had my details, from before I was married, how, this I don't know. I went into the branch, opened my account (with my marriage certificate), and received an sms the next day to say, Welcome to FNB Miss Pretorius. I'm Mrs Stoltz for the past 9 years. After this I lodged a complaint, where a consultant phoned me to assure me that my details on the system is now Mrs Stoltz. Today I received a statement from FNB addressed to Miss Pretorius. I need a manager to contact me to tell me where did they get my ****en surname details from, and why they have it because this is in contravention with the POPI act. They should not have any details of mine prior to me being married. Then, they have to explain to me how we can rectify this situation. Wow, such bad service, and I opened my account as Mrs Stoltz. How is this working? You can please contact me for my details.