"I have done the fake cut off by just hanging up in mid sentence. Politely because it's me talking when I do it."
Realistically, this is probably not something that I should be endorsing. And of course, it's a move that's been covered almost to exhaustion in TV comedies. But, because it's the weekend and because sometimes you just really, really need to get off the phone, I'm going to endorse it for certain situations. Of course, be sure to follow it up with an "I'm so sorry I think we got cut off, but I'll talk to you soon!" text. I'd also suggest trying to not make a habit out of it.
If you're reading this mom, sorry! We really did get cut off the other day.