What is the purpose of power attorney for according to Standard Bank? rd

I've had signing powers on my mom's account for more than 10years the reason being should there ever be time when I need to do something inside the bank on her behalf I can do this. This morning I went to the karaglen branch only to be told that I've done card replacement so all the cards were previously issued under her name and there's documentation that can prove this as this is not loaded on the system. So is it my fault that Standard did not capture the information on the system, when they closed the isando where we did wasn't this information supposed to be uploaded on the system to avoid inconvenience for the client. I was told sorry, bring her to correct the mistake can't help you. I've done transactions on her behalf before, done card replacements before. What is the point and purpose of power of attorney if I may ask. Cause the power attorney on there on the system according to the lady just not for me to do card replacement. So what is it for? If standard bank can help me out with this