Sims 3 Registration code already used

Okay, I need a tad bit of help, I don't know if I have done this incorrectly, or if I missed a step.
I purchased Sims 3 starter pack brand new. The first page told me to create a origin account (Trillian101712) and a Sims 3 account (Trillian1017)
It asked me to enter my serial code? The 20 digit number, and the only one I saw was the Sims 3 original game code, and I entered that. 
After completing my account and things of that nature, it said that Sims 3 was registered. As I went to install the disk, it went through normally until it asked me to enter my Sims 3 code, for the game to continue registration through origin ( yes, I was signed in). I entered the code and it said " This code has already been used" I am stuck there and do not know where to go further. I was told that sims3.com and origin.com were connected, and would transfer things, in which this did not happen. Is there anything you could do? Or do I need to return the game and get a new code, yada yada yada? 

Thank you for reading and I hope you can help me solve this issue. 
                                                                                                                   -Trillian1017.