I swear I read somewhere that Phasma is coming back in later movies. I mean, they really didn't show them cutting off any of her communications devices, she could have just radioed someone to turn off the trash compactor.
Oh, but that's already happened in a Star Wars movie. Can't have and pandering to nostalgia in any Star Wars movies.
Maybe...her armor is made out of adamantium and just broke the compactor when it tried to compact her.
If the people only understood the rank injustice of our money and banking systems, there would be a revolution before morning - Andrew Jackson