Estate late

my father passed away on the 16 August and we are trying to get informatin on his investment account at FNB and Mrs Koch at the Uitenhage branch is giving us the run around because we do not have the original ID we have deat and the birth and we even have the letter of authority from the Master of the high court. I do not understand why she cannot assist bcz we have all the necessary and we were helped at master without the ID