"Like I said..." in Chinese
Here is a full translation of your conversation.


  A: 我从没去过中国。
  B: 你对中国文化有什么看法
  A: 正如我说过的，我从没去过中国。


As you can see, "like I said" is "正如我说过的" in Chinese. A word-to-word translation would be 


  "like"  ⟶ "正如/就如/就像"
   I      ⟶ "我"
  "said"  ⟶ "说过的".