Can I Updgrade My Account?
You can add extra bandwidth or disk space to your account at any stage by logging in to your client area and navigating to Client Area >> My Hosting Packages >> Product Details.
Towards the bottom of that page is a text link: Account Addons - Click to view available addons, clicking this will bring up a list of available options.
Changing Plans
You may prefer to change hosting plans as opposed to adding additional resources, please open a support ticket to discuss the options available.