Not sure the correct (vs the easiest) way to do this...

[DanenRox]

Nevermind. Gonna take the high road.

 

[CarolynFH]

Nevermind. Gonna take the high road.

Changing the name of a guest can be done very easily online. Changing the name of the primary guest on a reservation (the first one on the list) is the only change that requires contacting MS.

ETA - LOL, you edited your post while I was typing mine! Hope mine helps you.