Why can't I change Microsoft account (Minecraft account) to my discord account

[6Cotton9]

Why can't I change my Microsoft account (Minecraft account) to my discord account because one of my account is connected to it and I'm trying to change the Minecraft account that is connected to the discord account with another Minecraft account I have one account that is named JNRZISFAT and one that is named 6Cotton9 and I want to change it to 6Cotton9 but how?

free plugins
minecraft paid for free
SpigotMC
minecraft plugins
mcmarket
mc-market
spigotmc
free minecraft paid plugins
free minecraft plugins
aac free
ewg free
Minecraft Premium Plugins
ewg free download
litebans free
epicworldgenerator free
free schematics
leaked schematics minecraft
schematics
schematics leaked
schematics free
minecraft schematics free
paid minecraft schematics free
paid minecraft schematics for free
free cracked plugins
free cracked minecraft plugins
plugins
featherboard download
featherboard plugin download
antiaura download
xenforo leaked
xenforo for free
xenforo addons