Every time I try to change the channel, it comes up with the messamge"this service is not available" I have to then switch tv off for few seconds then back on again! I only have freeview and its driving me mad !!!!
It appears that your set isn't receiving a strong enough signal from your aerial to 'lock onto' transmissions when you routinely change channels but the power surge from switching it off and on again gives it a little boost so that it can lock on.