There are two types of platysmaplasty- anterior platysmaplasty or corset platysmaplasty which is performed to improve platysma bands, and posterior platysmaplasty which involves posterior retraction of the neck muscles. The latter surgery can help efface the bands but will not eliminate them. There are roles for each type of operation depending on the goals of the surgery.
If you had a posterior retraction and not a corset platysmaplasty, combined with liposuction which removed the fat hiding the bands before surgery, the bands could appear worse after surgery.
Discuss your concerns with your surgeon, and find out more about your surgery. In a worst case scenario, a revision will likely fix anything that concerns you. Best case, swelling will go down and your neck will look great on its own!