Only admins can edit a deal's Actual Close Date — both on the deal profile and in list views.
The Actual Close Date is part of a deal's historical record. Keeping edits with admins prevents closed results being reshaped after the fact, which matters when commission or reporting depends on them.
The date is set for you. Moving a deal into a won or lost stage fills in the Actual Close Date automatically — so if it's wrong, an admin has to correct it. See Change a Deal's Stage.
If you need a date changed and you're not an admin, ask one of your account admins rather than support — they can edit it directly.
Need help? Contact support at customercare@pipelinecrm.com.