pace reciever says 'no signal' when changing channels?

my pace 1.3.36 digibox from sky is about ten years old and has always been good up until the viewing cards where changed over.
I keep getting a 'NO SATELLITE SIGNAL IS BEING RECIEVED' message when i go to change channels alot of the time. They do come back eventually but im paying for a service i am not recieving !! i have phoned sky and they want £65.00 to put it right and i think that they are ripping me of unlike many others. surely it should be done for free as this problem has only occured since then. i have heard that you can access a hiddin menu on them to update the software, is this true. if you can help me i will be able to cancel and un nesscessary appointment and hefty fee....