I am wanting to build my own custom phone case (yes dull but I

I am wanting to build my own custom phone case (yes dull but I want my own design). A relative has access to a 3D printer but need someone who can take a paper drawing and turn in into a .stl file to print from. Any ideas?

I use inkscape to convert paper to dxf. That tool is free. Then I use openSCAD to extrude these shapes to make a design.

To answer you question I don’t know who will do that for you

Heh - there are people who can do that but you may be expected to pay something. They’ll probably want to look at your drawing before committing to a quote because from my experience, people who don’t own 3D printers or use them regularly often have very unrealistic ideas of what can be achieved.
But on another note, you are taking out the best bit of the process, learning to build a model for yourself!!!. There is plenty of opensource software you can use and free iPhone ‘templates’ you can base your model on (or customize). Tutorials are freely available, so why not have a go ?

Camerin’s method is a great place to start. Have a read of this:

you could just use sketchup, and follow tutorials to learn it. Shouldnt take more than a day to learn enough to do this. Then google stl export plugin sketchup, and install the plugin and export.

What type of phone?

Lots of good advice. thanks all.