HOW DO I CHANGE CORE SIZE FROM 16 TO 4

Hello, we installed Windows Server 2016 and SQL Enterprise on a Dell PowerEdge R440 with TWO Intel Xeon Silver 4208 2.1G, 8C/16T, 9.6GT/s, 11M Cache, Turbo, HT (85W) DDR4-2400
 CPUs.

I was doing annual MS True up and the sticker price for SQL Enterprise for 16 cores is $52K.  We don't have that money budgeted.

How can I reduce the number of cores to 4 so we reduce the cost of the true up?

Can I do this on a server in production?

Is this a setting in SQL server or BIOS?  I don't want to reduce the cores for the O/S.

Thank You.