Chances are the guide was written ages ago and hasn’t really been kept current, it’s been years ( possibly decades ) since ( from a billing point of view ) that there was any difference between a local call and a national call ( a national call where the STD code was necessary, a local calls no code , just the phone number , and adjacent area calls ( via a short code not the STD code )
DV and quite a few PSTN exchanges require the STD code for local calls as well as ‘national’ calls so it depends if the barring is sophisticated enough to realise using the STD code for ‘local’ calls is still a local call ( I suspect it will be )
….TBH , it probably is necessary to try ‘342’ and make a local call , ( using the STD code if that’s necessary in your exchange area ) and then confirming connection, if it doesn’t connect then there isn’t really any difference between 342 and 341 .
FWIW , with BT plans , PAYG and unlimited, call baring is not as useful as it would have been historically, as a call to a mobile ,a local call , or national number are the same cost per minute or included in the plan so stopping a ‘national’ call but allowing local calls is somewhat redundant.
The primary reason for call barring was to stop expensive calls being made , and not a way to restricting a person from making calls for other reasons apart from cost .
AFAIK , there is a restriction where 10 numbers are allowed and no others .
