'Could you please connect me to the telephone number 9999999?'
'Certainly sir. Bear with me please.' ...
[Ten minutes of canned music later:]
'I've been waiting for ages. Can you connect me to the telephone number 9999999?'
The other thing about 'can' is that it can be interpreted as referring simply to ability. (So could 'could', but its use in polite requests makes it less likely to be misinterpreted.) For example, when I saw your question ('Can someone explain this to me...?') I thought 'I don't know - can I?' Let me know if I've managed!
Student or Learner