They shouldn't do that. If you purchased from a dealer, it's under warranty so you can take it back and have it fixed.

10mm socket

Get a wrench and turn clockwise.

There are adjustments made to the friction of the joint that allows for movement. when you tighten that adjustable screw or nut than the effort to move the and alighn the mirror so that it stays in the location anyone who drives the vehicle can move it where it suits them.

Had the dealer do this and the mirror still moves around.

Mirrors with turn signals
 

If your mirrors are the type that have the turn signal in them, you need to be careful tightening the nut. I used a pair of needle nose pliers to tighten ours and broke the wire to the signal. Now that we have it fixed, I will only use a socket to tighten them.

time for someone new..... it works 100 percent of the time