Why offer same day delivery when you can't fulfill it

What's the point in offering same day delivery if you cannot fulfill the order.

I followed all the requirements, made sure all items were in stock at my closest warehouse, placed and paid for the order before 10am,it was 3 small items.

Before getting into anything below, not I was not informed that my delivery date had changed if I did not check the tracking I would not have known.

I call and I get told an email will be sent to the warehouse, next person tells me I didn't select the same day which was confirmed after that I did but cannot guarantee delivery today. I was still calm and but a third person calls tries and make it as if I don't know what I am talking about and said it might be a system glitch that they can only sort out the issue after the delivery happens that just ****ed me the hell off. Why do you have the option then cannot keep to it or inform the customer but when we try and find out what's happening we made to feel stupid.

What kind of service is this, from 10am till the time I post this (15:26) I am still waiting for some sort of answer. Now I have to make arrangements for someone to be available or change my plans for tomorrow when I am supposed to be leaving on holiday just so I don't loose out because by the other posts it's not like a refund will happen over night if I cancel the order.