In stock when it's actually not!!

So my girlfriend ordered me a smart bracelet as a gift and a token of her appreciation for everything I have helped her gotten through so she ordered me one with Bluetooth earphones and she asked me whst color I want and I wanted the blue ones so she chose the blue ones and it showed that there was stock so she ordered and paid for them only to be told now that they don't have stock of those blue ones and that they are going to have to get some of them and also they didn't offer her a change in color for something they do have, as a consumer I do find this unacceptable, if you don't have something in stock in that color, atleast give the option to change the color instead, I mean it is paid for, what difference would it make just for that extra bit of service?