I can think of 2 clunky brute force ways to do it.

1. add dummy rows with values for Y that extend the Y scale where you need it, exclude but do NOT hide the rows, run the control chart, then hide the rows.

2. use just the original data and run the control chart, then use the cross hair tool to determine the X values for the phase dividing lines (it may help to enlarge the plot first) which will have values n.5 where n is the row number of the last row of the previous phase being plotted, then edit the X axis to add reference lines for each dividing line.

Michael