I'm here to provide some additional insight into eliminating the Product/Service column within an Invoice and Estimate. Since you already have information within the Product/Service, then you'll need to delete that information, set the setting for that sales form, and then save the changes. Here's how:
Go to the Customers tab.
Select the All Sales section.
Pick an Invoice or Estimate that you'd like to change.
Once on the sales form, click the Product/ Service box that you already have information in and backspace until empty.
Press the Gear icon in the top right-hand corner of the form.
Uncheck the box beside of Product/Service and then hit the "X" (Exit symbol)
After you're done with all changes select Save and Close or Save and New.
You'll need to do the steps above to each sales form with information already in the Product/Service column.
Afterward, I recommend turning off the Product/Service option in your account settings so that future sales forms won't have this feature. Below are instructions on how to turn off the option.