Remove User Sitemap from XML Sitemap index

Hello, I am using your incredible plugin. Thanks for this.

In my xml sitemap I have:
post
page
user

the last one “user” link to sitemap-user.xml a 404 page
i want to remove it and leave on my sitemap index only:

post
page

could you help me to achieve this?
I tried different codes into my functions.php without to find a one who fix this issue.

thanks for your help