If you were actually charged for the mini and contacted Google support they will ask what the promotion code was. For myself and many others there was no code, only a link to follow and a pop-up saying the discount would be added during checkout. Google has offered to help return the device but will not reimburse you for the promotional discount.
Re: Google Home Mini Promotion still trying to charge full price?
I did it... And hours later Google cancelled the order, later by phone they ask me to place a new order and I did...oh surprise 52.43$ were charged to my credit card... I call and ask for the refund and wrote about 8 different email both Google and Spotify support stating my case... 48hrs later I haven't received any solution... I wonder if I call Apple store and tell them I would like to change to iPhone and all the other services associated with them... They may even use my case to advertise how to do something wrong! And how to get a customer well treated.