Service delivery or should I say lack off...

A minute or 2 after placing and order I tried to change a delivery address with absolute no luck and be told it cannot be done... There after I tried to cancel the order and guess what the same response cancelation cannot be done... This for me is the first delivery service where a delivery address cannot be changed... Why would this be the case that a simple case of change of address cannot be done.... It is absolutely rediculas that Mr Delivery is will not to help you when something goes wrong...