It may be rude but it's not always immature.
If you call someone up and they curse you up and down you have every reason to cut off that conversation.
If a telemarketer calls you during the middle of dinner and (you tell them you're not interested) but they insist on continuing to talk, you have every right to end his/her interruption of your evening.
If someone makes a prank or obscene call to your home you are not obligated to hear every vile word that spews out of their mouth.
Naturally if you are having a disagreement with someone that is escalating ideally it would be nice to tell them you'd like to pick up the topic at another time, or if you have been going in circles covering the same stuff and the other person will not let you go.
Some people simply refuse to stop beating a dead horse!
Your options are to put your phone on mute and walk away or hang up.
Either way you have a right not to be "bullied or held hostage" over the phone.
Sometimes you have to match rudeness with rudeness.