It's not really getting murky for government prisons.
Free speech allows you to speak. It doesn't guarantee that your message will be delivered remotely to a distant place.
People seem to not understand that transporting messages (eg. a letter, or keeping a phone service) is not part of speech. It's part of a delivery job. And free speech in the constitution does not warrant access to a delivery person, nor does it prevent the government from taking away access to such delivery people. Therefore you may be allowed to speak and write letters, but no one needs to accomodate you and pass on what you spoke or wrote to anyone else.
Therefore your family, to be guaranteed having the ability to receive your message, must be within an earshot of where you are in the prison at the time.
Literally every divergence from this has nothing to do with constitution and everything to do with other laws. If anyone tells you otherwise, then they do not understand English language. Yes, this also applies to courts 'interpretations'. They may be lying, they may be misunderstanding. But in the end, they are simply wrong. Atoms don't stop existing just cause someone said there's nothing smaller than bacteria.
