Why does an invoice, recorded as a sale, show up in services under a Profit and Loss report? The invoice in question was paid via EMT, but will not link to the invoice.

Here's what I have done to try and recreate the issue:

- I recorded a sale that was performed prior to starting to use QuickBooks. 
- I added a new invoice, recorded all of the information, attached a copy of the old invoice.
- I clicked on "recieve payment", went through the steps, once finished, noticed under the Profit and Loss report, that the invoice was recorded under Services.
- I then recorded the Email Money Transfer that I recieved from my customer as a sale, and used a reference number, which I also used on the invoice for the sale.

The problem:
Now, under Profit and Loss in Reports, I see income under Sales (linked to the email money transfer). I also see income under Services, with the invoice in question. I would like to see that invoice under Sales only, not under Services, but I do not know how to make this happen.

Thanks in Advanced.