Worst service ever

Today I visited the Woolworths store at Carnival Mall. I had to buy a present for a cousin on my mothers behalf for a bachalorette party. My mom is ubable to do the shopping herself as she has cancer she is wheel chaired based but mostly bed ridden. She asked me her daughter to go and buy these things on her account this is not the first time I am doing this for her though. As per usual she writes a confirmation letter to confirm that she gives me authority to do so with her Id and my id. I got to the till to do the payment where the lady then refused to assist me stating that I am not allowed but just a few weeks before I dis exactly the same thing and had no issues. I said to the lady behind the counter why is it now a issue they can phone my mom if need to, she refused and kept on saying that my mom needs to be present. The more im trying to explain to her that its not possible my mom cant walk she is bed based. She refused. I asked to have the manager called. After waiting for ages. I then told the lady you know what just put it on my account I dont have time. I took my card out gave it to her, she turned to me and said to are you sure this is your account can I please your id. I completely lost it. I do not appreciate the way I was treated and the fact that they would not assist me with my moms stuff and the way they assisted she must be present. They had no sympathy with the situation or even tried to see how they could help. This was really shocking service.