Changing effecitve date of plan added to program

I am hoping that someone can provide assistance. While completing set ups for Open Enrollment, I mistakenly added a plan to our program with an incorrect date. How do I either change the effective date of this plan being added to the program or remove the plan from the program.

When I try and date track back to the correct date and add the plan I am getting a message that says that there the plan is already associated with the program. When the list is queried, the plan in question does not show up.

Any help would be greatly appreciated.