Sure, you can make a 2D map with the system, but you will still need a 3D program to UV all the 'quads' to match your tile set.
This shouldn't be very difficult.
...and you don't need Maya specifically, you can use any 3D program (including Blender which is free).
For example if your tile set is 20 x 20:
- make a plane
- subdivide it 20 x 20
- make sure the uv's of the entire plane map to 0 - 1 (at this point the sections of the plane should look like the tiles)
- then place it so that the corner of the plane that maps to 0,0 is at 0,0,0 in the world.
- then split off each quad of the plane (in Maya the commands would be: mesh > extract, this separates the faces then mesh > separate, to turn them into separate objects )
- center pivot for all the sections
- just to be safe, reset transformations for all the sections
- then use it in unity!
I was even considering to offer to do this for you since it's pretty simple, but I think it is a good idea for you to know how because it's highly likely you will need to modify the meshes at some point.
If you do decide to get a refund you have to talk to the people in the Unity Asset Store (as a dev I don't have access to any of your information or payment etc).
But anyway, let me know if i can help you more: The easiest tile set of all to make is a 2D one!