Once an Ad hoc Supplier is created, to update the name of the supplier:
Click the Admin Cogs
icon, then on the left, click Suppliers.On the left, click Manage suppliers stay on the Current tab, search for the Ad Hoc supplier group.
On the right, click View Ad Hoc Suppliers which is the Brown Folder icon.
Locate the supplier and on the right, click Edit and update the Name as required and finally click Update to save changes.