LIbraRy telephone notifications

So yes of course I am thankful for the library. But you will notice that their computer generated telephone notifications are impossible to dismiss...... In other words, you cannot hang up on these calls because they do not disengage until the message completes in full. How is this possible? Hanging up on every other call yields a dial tone right away but not with these calls. How do they manipulate our telephones exactly?

Not only that, but if you try to hang up part way thru the call, the whole fing MSG repeats again right from the beginning!

What technology are they using to keep people hostage to their notifications?