If you are under a Radar Advisory (IFR) or Radar Information Service (IFR or VFR), then we'll always try and hand you over to the next radar unit.
All the silences you may get when you make a transmission are not just the atco refusing to talk to you, usually they're on the telephone coordinating.
If you're under a Flight Information Service, you'll not be positively identified, and you're quite likely to be one of many aircraft in the vicinity, most which will be squawking 7000.
Aircraft operating under a FIS will not usually be handed over due to the time involved in making the telephone call and passing on all the details, added to which, the pilot has no obligation to then contact the next atc unit.
There are odd exceptions to this, (aircraft operating over the sea to/from the UK etc).
A visit to your local radar equipped atc unit will open your eyes.
