If you and your spouse came up with a custody plan that works for you, it might be disruptive if they suddenly want to change it. While many of the changes that people want to make might not be warranted, modifications for purposes such as moving or letting your child go to a new school may be necessary.
If you and your ex-spouse are able, one of the things you can do is to sit down and discuss a new custody plan. Together, you may realize that the current plan is not working or that your child's needs are outgrowing it. If that's the case, then you may want to look into working out a temporary plan. With your new plan, you can make the changes that are needed in the short term, but you should also reach out to your attorney to seek a modification in court, so that the changes are legally binding.