Mac Mini 2018 SSD upgraded by Apple after purchase

It is unlikely, but not impossible that Apple will do anything about this. Any product configuration terms that were in effect when you purchased the mini will likely stand. You could have used the 14-day (U.S.) return policy when you received the mini, and then ordered another Mac mini under the new offer — but apparently you did not.

If you haven't damaged the computer in anyway Apple's return policy is that you can return it within 2 weeks if you bring everything back that came with the box.

Apple is very leniant with their returns policy and I haven't come across another company with a "try and buy" policy like theirs. Usually, as soon as the box has been opened, most policies state that you can't return it unless it's faulty.

You could buy a new car, fridge or washing machine and the next day a new model could come out - just a fact of life.

Hello,

You will need to call Apple for assistance.

Contact AppleCare