If your neck hurts can be because of 2 main problems... a core problem or a fit problem

If the saddle is in the wrong position is clear where the problem is coming from, no idea what bike are we talking about here too.

I was you i would start with the most simple of the things, post a picture of the bike it self and one with you riding it. Interesting to see a fit thread but help is pretty much useless w/o pictures.

Good luck