I would probably use a couple of Subreports for this (easier option).

You could build a query that has all the required fields from the necessary tables and set up
Grouping levels both services and products.

Does the Combine Reports help you?
Just don't put in the page break.

You could also union them together.

Hey Guys, is they an Seminar or Course on Reports?

No - not specifically on reports.  Reporting  is covered through out the courses and TechHelp as needed or to show different techniques.
If you take a look at the Microsoft Access Outlines and search report (Ctrl-F) you will get 328 matches.
Do you have something in mind?

Richard, I have  "Invoice Details Query" that have that we calculate all the"Sale Taxes, Subtotal, Discount, and Complete Invoice Total ". Also, I have an "Invoice Info Query" has everything: the InvoiceT and the InvoiceDetailT. Trying to figure out the way to display the "Products and the Services" in the Same Reports?

Hey Crew, I think I have it... I just got it to display the right Customer for the "Invoice Detail Form".

That's good  news!  
Once you have it working you might post a "here was my issue and this is how I did it" just in case others might find it of use.