john-pero's answer should help you merge two names successfully. I'd be glad to walk you through the detailed steps so you'll be able to merge the names.
When merging two names, you'll need to make it similar to the contractor you're merging it with. Here's how:
From the left menu, click Expenses.
Choose the Vendors tab.
Select the name of the contractor, then click Edit.
Make sure to change the Title, First name, Middle name, and the Last name that similar to the contractor you're merging it with.