PremiumWP

It depends on your theme or mobile plugin whether your website has a mobile version. There is no mobile switch or button in the WordPress software itself.

You need to use either a responsive theme or a mobile plugin.

You’re going to have to provide a bit more detail so people can try to answer your question.

The width of your sidebar is only 240px. The banner extends a bit wider than that but then is cut when it reaches the extent of the page wrapper:

I would suggest using a different banner because 300px is just too wide for your sidebar and will look odd if it’s actually that wide.

Otherwise if you don’t mind making your sidebar wider and the whole site wider you can change the widths as shown below:

#page .wrapper {
    background: url("images/wrapper_bg.png") repeat-x scroll 0 0 #F5F5F5;
    margin: 0 auto;
    position: relative;
    width: 1060px;
}

#secondary {
    float: right;
    margin: 10px 20px 0 0;
    width: 300px;
}

However you will then have to fix other style elements also to make them wider to match, such as nav bar etc.

You can use a tool such as Firebug to help in making style changes to you site.

Looking at the page source code it appears to be using this plugin: http://wordpress.org/extend/plugins/grunion-contact-form/

Maybe have a look through the free themes directory first: http://wordpress.org/extend/themes/

Also have a look at the themes from the premium / commercial providers who have more professional business style themes

As its a commercial theme which includes support in the purchase price the best place for help with your theme is from the developer.

WordPress themes on WordPress.org are required to have a GPL license and this needs to be stated in the theme files. See info about licensing here: http://codex.wordpress.org/Theme_Review#Licensing

As it’s a commercial theme which includes support in the purchase price you will need to seek support from the developer.