People always hang up the phone without saying goodbye or anything. I read that it's some time is money thing in film and TV but it just sounds like bullshit to me.
TV shows and movies only make you think it's a cultural thing.
We say "bye" here in the US after essentially every phone call otherwise people would probably be confused at when the conversation ended or when you're hanging up.
An exception I've had to this is when I'm getting a phone call where someone is trying to meet me at a location. I might hang up without saying bye if we both make eye contact in person and find each other. Because we're going to continue the conversation in person anyway.
There are other rare exceptions like this, but it's definitely culturally expected for you to say "bye" before hanging up!
I would love to hang up without a goodbye, but then people are just going to call me back because they'll think the call dropped. After a couple of those awkward interactions, I would quickly switch back to some sort of affirmative close to the call.
I had a boss who did this! He just abruptly hung up when he was done with the conversation. People used to call back, worried they'd been cut off, or my boss was mad at them. Nope, he's just overly autistic-efficient.