To start with, 'Brenda' will be an anglicised name because the chances are, you are speaking to a call centre in the Indian sub-continent, and they are advised that an English name has twin benefits - it helps to distract you from the fact that you are dealing with an off-shore call centre which means that she is doing the job for a fraction of what a UK operativre would cost - and who cares about trhe problems you have had because ... Vshe is doing the job for a fraction of what a UK operativre would cost! Plus there is a good chance that this lady's actual name would be unrponouncable anyway!
OK - now to your issues.
These personel are specifically trained in the most common functions that the average caller wishes to peform, and to that end, they are trained using a script. if the customer mentions any key words that refer to a section of the script, the operative will head for that section of the script and begin quoting. That's why you almost got your accounts by the operative - she is not actually following what you ask, she is following her script.
Similarly, they are mandated with attempting to sell every caller some insurance, or an upgraded account of one sort or another - again this is scripted, which is why your denials are ignored.
Of course, there is a very simple way to avoid your frustration, which is for your bank to employ UK staff who speak English as their first language but of course ... refer back to my first point.
For heavens sake - what do you want - a 'Help Desk' that can do what its desription infers, or an eight-figure bonus for the chairman?
You need to adjust your priorities milly!