Subdomain always redirect to WWW (home page) - wordpress

Question

I want, when open subdomain to return existing Wordpress page ex. www.example.com/custom-wordpress-page.
Server OS is CentOS 6.6, while Web Server (httpd) is Apache 2.2.15.
It have installed and configured Wordpress with .htaccess files configured for it's mod_rewrite.
Root folder is /var/www/html.
.htaccess file is in /var/www/html/.htaccess :
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
This configuration is working very well with one domain (ex. example.com). Today I wanted to add subdomain (ex. subdomain.example.com).
I tried multiple solutions including VirtualHosts with/without NameVirtualHost in httpd.conf file, also adding RewrriteCond&RewriteRule
under mod_rewrite in .htaccess file.
NameVirtualHost *:80
<VirtualHost *:80>
ServerAdmin email-address-redacted
ServerName www.example.com
ServerAlias example.com
DocumentRoot /var/www/html
</VirtualHost>
<VirtualHost *:80>
ServerAdmin email-address-redacted
ServerName subdomain.example.com
ServerAlias subdomain.example.com
Redirect permanent / http://example.com/custom-wordpress-page
</VirtualHost>
Also in first VirtualHost, I tried *.example.com instead off www.example.com.
In second one, I tried to make Reverse Proxy using ProxyPass and ProxyPassReverse.
Instead of using :*80 I tried using IP address of server and domain name.
Using .htaccess Rewrite rule with/without VirtualHosts gave no results.
subdomain.example.com always opens www.example.com instead of www.example.com/custom-wordpress-page.
Keep in mind - there is a lot of threads like this, but I tried many of them, including many tutorials but they aren't working alongside Wordpress.
Edit : Want to add that there are no wildcards in DNS records. There are NS records, one A record for example.com, one A record for subdomain.example.com and CNAME record for www that is poiting to example.com. There are NO *.

Answer 1

There was problem with hosting provider DNS records, configuration was correct, but I had to call provider to check records in their system and fix what is broken. After they done their job, it works correctly.