My galaxy note 10.1 has suddenly lost service connection?

24 hours this tablet was happily transmitting info back and forth then suddenly I received a warning saying I'D LOST SERVICE. I left it for a few hours thinking the supplier was doing an update or something. This morning was still the same. I called the help desk at Samsung after midday and was in the middle of describing the problem when the device started sending all the notifications that had backed up. However the triangular flag at the top right hand corner was grey in colour and no bars showing. The transmission ceased and a circle with a line through it re appeared. Could you please point me in the right direction