Please note I'm not a teacher.
The Present Perfect is not normally used with words that refer to a finished period of time, like yesterday, 5 minutes ago, last month, in 1999, when I was a child etc. This is because the Present Perfect focuses on the present, and words like these focus on the past.
So, in your case, you should use the Past Simple (last October is a reference to the past)
Student or Learner