Subdomain Directory problem

[Hi5technology]

i am using plesk panel 11.0 , i have created subdomain for abc.com as demo.abc.com, when i click to manage subdomain i got error as follows Error: Unable to change directory to //demo: Directory does not exist. , and showing abc.com domain httpdocs directory ... when i asked hosting support they told me as in plesk 11.0 you can't manage subdomain via plesk , you have to create directory for subdomain in abc.com and upload files into that folder , then manually you have to copy files to suddomain httpdocs .. is this true? give me some solution .