I am not a teacher.
There is (or was) a real difference between "may" and "can" which is in danger of disappearing.
May I speak to Mr X? (with a capital "I") is asking permission, or enquiring about the possibility of speaking to Mr X.
Can I speak to Mr X? has come to mean the same thing, but is actually asking whether you have the ablility to speak to him.
Student or Learner