Jan, Welcome to Cruise-Chat!
Yes as Larry said there is a service.
But, there are regular old fashioned laundrette areas on some decks as well. Washer/Dryer and Ironing facilities.
Here is a link for you:
http://carnival.com/CMS/FAQs/Laundry_Facilities_-_Self_...ce_Launderettes.aspx
Hope this helps, and again Welcome Aboard!
IslandCruz