AddRAM said:
Refuse delivery, and order the right memory.

Or just send it back, there should be no problem, it will be less than 15 days and you didn`t open it.

If you call them , they will also tell you to refuse delivery.

There should be no questions asked, just tell them you made a mistake and ordered the wrong memory

If you keep it and install it, all your memory will run at the slower speed.
Thanks. I believe that this would be the most expedient. I'll just order more of the same that I ordered, and taken the old memory and save it for another DDR4 build. Thanks man. And thanks to all of you for the help.