Poor customer service - online delivery

I placed an online order on 29 July - chose 1-3 days for delivery. Which means it should be delivered today, thought everything was on track as my order says SHIPPED for the last few days. I followed up on my order only to be told delivery will take place August 6th - that’s double the amount of days. Why can we chose our delivery lead time of its never delivered in time. Every time this happens - which is almost with every order I have to follow up - there’s never communication from Mr Price. Now I have to return everything as I needed them for Sunday Al- hence me choosing 1-3 days. Once again disappointed.