It is a popular misconception that the only way to remove dreadlocs is to cut them off or just shave your head. However it is indeed possible, although it does take time and effort, nor is it guaranteed to work out perfectly.
First, schedule time to do it. You might even need multiple consecutive days. Your hair may have been tangling up for years and it won't come undone quickly. If you have friends that can help you, that not only speeds up the process, but makes it much easier to reach locs in the back of your head.
Have on hand the tools you need, which is access to lots of water and conditioner, plus combs, brushes and rat-tail combs. Expect at least one or two rat-tail combs to break. A spray water bottle is also useful.
Wash your hair to start the process, but try not to dry it much. You need your hair as wet as possible for as long as possible. Reinforce the moisture of a single loc and then apply conditioner to it. Using the pointy end of a rat-tail comb, proceed to gently start picking out the end or bottom of a loc. Use more water and conditioner as is needed.
Don't panic if you lose any hair during this process. You likely have years worth of already shed hair in the locs.
Once the end of the loc is free, moisturize the local hair again and comb it all out.
Repeat these steps for all your other locs. Once your whole head is done, wash it all again and brush well. Depending on what is left and how long it is, figure out a hairstyle or braiding pattern.
Now, take a nap or have a party with the friends that helped, maybe both.