My credit went to another person with the same name

Start from the  main page for Bad Fellaz (2015) and click the Edit page button near the bottom.

Select Correct / Delete from the dropdown beside Cast (the first item)
Click Continue (at the bottom of the page)

Change the Keep: to Correct in the Action column beside Lyon, Justin
Click Check these updates

Change the name to Lyon, Justin (II)
Check the box beside provide an explanation to assist in processing this change
Click Re-check these updates

You will see a warning message starting :

This credit has warnings, you must acknowledge each one before this credit will be accepted.

followed by several options.
Select the radio button beside This is a different person not currently listed - create 'Lyon, Justin (II)'.
Enter the explanation . Something like

I am Justin Lyon and I performed the part of Carlos in this film. This is my first credit. I am not the Justin Lyon already on IMDb so I am moving this credit to a new name page

Click Re-check these updates

The item background should now be green, and you can Submit these updates.

Changes like this usually happen in a couple of days, but can take a week or even longer.