The problem is the structure of your data. You have an X variable and you have a Y variable. You also have another variable that indicates which series it is, either A or B. Thinking that way, you see that your data needs to be structured differently. You need to stack the X and Y variables.
I made a sample dataset to mimic your situation (attached) with random data except for the X-axis. The data table has four columns, SeriesA X, SeriesA Y, SeriesB X, and SeriesB Y. I only put in series A and B, but you could extend to series C if needed. I then went to Tables > Stack Columns and completed the dialog as follows:
This will give me a table that has 4 columns (Group, X, Group 2, and X 2). You can rename the X 2 column to be Y, if you want as it does contain the Y values. Now go to Graph Builder. Drag X 2 (or Y if you renamed it) to the Y-axis. Drag X to the X-axis. Drag Group to the Overlay area. You might want to do some clean up as the Group column will say SeriesA X and SeriesB X when it really only needs to be an A or a B, but I think this is the picture that you are looking for. This final data table with a script for the graph is also attached.
Dan Obermiller