Windows Product Key

After weeks trying to fix my laptop, 2 callouts and then sent back for repairs, they eventually returned it  today. They have installed Windows 8 again but have not given me the new product key.  Tried phoning, they are closed, sent emails, but they never reply the same day.  Tried online chatting but won't recognise my service tag, even though I can log in with it.  Fuming as I expect nothing will be done until Monday. Will anyone from Dell contact me?!!!!