Open the job and press Edit at the top right. Change the pickup or delivery name, address, contact, phone or email, the Ready from and Deliver by times, the service, dangerous goods, after hours, tail-lift, hand unload or the notes, then press Save changes. Only what you changed is saved, the timeline records it, and the driver app shows it at once.
Jobs can be edited until they are picked up; after that Edit is greyed out and only the price can change (until the job is invoiced). Items and the customer cannot be changed: cancel the job and book it again.