No Customer Service

A transaction went off my account without requesting an OTP. I went into a branch and they could not give me an explanation. I have phoned FNB and I keep on getting transferred with no answers. WORST SERVICE I have ever received from a bank. I received an email to say someone will contact me within 24 hours but it's been a whole week and no phone call. Please could somebody from FNB contact me and explain to me how this happened?