[Plugin: WooCommerce – excelling eCommerce] Disable quantities

In your admin, WooCommerce->Settings->Inventory: Untick the checkbox option for “Enable stock management” next to Manage stock, then in the product edit screen in the Product Type box, tick the Virtual or Downloadable checkbox (depending on what you sell obviously).

Then select the inventory tab in the Product Data box, make sure the Manage Stock checkbox is unticked.

Hope that helps