Can anyone recommend: Aluminium Carpenter / Sliding Glass door repair

I am looking for a recommendation for a RELIABLE tradesperson / Company that can repair the sliding glass with aluminium frame doors.
Ours is sitting at an angle and doesn't seal at the top.  I have had the door out and tried to adjust the wheels, but it still won't seal, so need a professional to look at it.

By "reliable" I mean 

• Someone who actually responds to messages
  
• Someone who will answer the phone
• Someone who will come out when they say they are going to or indeed someone who will actually bother to turn up at all.