Service Complaint

I’ve been awaiting feedback/assistance for over a week now on a complaint that I was assured would be looked into. Sibahle from FNB called last week to say she would be updating yet nothing is happening. She further advised I can use the chat facility which I did and Nokthula said they can’t help with my query. What does one have to do to assistance and resolution from FNB?? Is the a main branch to go to? Or what