Push.. push.. and push....
You don't get any reply to your emails.. so you phone... you don't get any answer to your phone calls, so you leave messages..
My internal examiner was really busy, she took 5 weeks to send me my corrections and then decided to have a holiday like.. 'now', before writing to the exams office, saying she had accepted my corrections... I had to push and push and get my 2nd Supervisor to basically camp outside her door and bug her outside of work... and she finally did what was required.
There is, of course a limit... too much pushing and they'll hate you - but I've found that with some busy people, you need to always take the lead and be proactive.. and when you DO have them on the phone... make sure you schedule a phone call catch up on 'X' date.. that way you know when you'll next speak to them and if they cancel, ask them for another date there and then....