site not opening with www and .htaccess file is not working

Hi my site opening without www http://theaffordableseoservices.biz/ this should be open with www like http://www.theaffordableseoservices.biz/ for this i have used .htaccess file with following line but that is not working

RewriteEngine On

RewriteCond %{HTTP_HOST} ^([^/.]+)\.theaffordableseoservices\.[^/.]+$
RewriteCond %1 !^(www|str)$
RewriteRule ^ http://www.theaffordableseoservices.biz%{REQUEST_URI} [L,R=301]
RewriteCond %{HTTP_HOST} ^([^/.]+)\.theaffordableseoservices\.([^/.]+)$
RewriteCond %2 !=com
RewriteRule ^ http://%1.theaffordableseoservices.biz%{REQUEST_URI} [L,R=301]

 

I link with WWW in it works for me. I don't what error you're receiving.