Why would they give me an incompatible receiver?

I recently purchased a 3D television (Samsung PN50C8000) and specifically ordered Direct TV for their 3D channels. I had the satellite installed on Saturday, and I just realized that I cannot access the 3D channels because the receiver Direct TV gave me (H20) is not compatible with 3D channels. Apparently you need an H21 or higher to access these channels, so my question is: why would they give me an H20 when they knew I would need an H21 for the 3D channels? I am very upset about this and would like to know what can be done to correct this. I dont feel that I should have to pay for a new receiver when I just got this one installed to begin with. Any advice you can give me would be greatly appreciated.