Help :( PLEASE - Wall Thickness

I am currently working on a model of the school I recently graduated from (The Fashion Institute of Design and Merchandising) This is my first model that I am getting printed, but I guess the walls are still too thin. I've done everything I can think of to try and fix it, but I am still very confused as to how exactly the "thin walls" and "wire" work. If someone could take a look at my model (modeled in Maya) I would GREATLY appreciate it. I need it printed ASAP. I've submitted it about 3 times and all 3 times they didn't pass. I am starting to get discouraged because this peace is very meaningful to me.

I can't open your MB file. What file format did you use to upload to Shapeways?
If you can export to an STL, OBJ, or DWG file I will have a look.

Thank you! Here is the .obj file

What size is it supposed to be?

About:
Length 12cm
Width 5cm
Height 6cm

The base is about the size of an iPhone 5

The file is now fixed.
It is a bit expensive with the internal wall where it is. I will try to make it a bit cheaper for you.

Thank you so much! I can't thank you enough. Will the inside be solid?

That is what is making it expensive the top part is solid. I will try to make the walls 1mm thick.
Shapeways charges by the volume of material used cm3

Oh okay. Thank you again for helping me out! I really appreciate it. This model will be going on top of my graduation cap. I wanted to use the Ultra Detail, but at this point I will settle for whatever is cheapest.

I have tried to hollow the model with Blender. It may be rejected by Shapeways.

What was I doing incorrectly?

The internal floor was creating the solid, The walls were a bit too thick.
I just deleted all of the internal walls and floors. Filled the whole floor in at the bottom so the model was completely solid. Imported into Blender then used the 'Solidify Modifier' to create a wall thickness. Exported as STL. Opened in Netfabb. Deleted the bottom floors, then created new faces to join the inner wall to the outer wall. The only problem is Blender does not do a really good job at keeping the wall thickness uniform, It varies so some parts may be below the minimum wall thickness.
A bit convoluted but it usually works.

Oh okay that makes sense. I thought I'd be able to get away with hollowing it out the way I did, but I guess not. I tried going the "Extruding" route, but Maya was being difficult. I really hope it works.

Hey! It worked! My model is in production So excited. Thank you again