Translation:The cell phone is old.
In North Korea, both 휴대전화 and 휴대폰 are used, despite the latter being a partially English word (contrary to popular belief, there is quite a few of English loanwords in Northern dialect: 샤쯔 for shirt, 엘레베터 for elevator, 라지오 for radio, 진즈 for jeans etc. etc. Still, far less than in the South).
There is also a funny word '손전화' which literally means a "hand (손) phone (전화)". It's unique to North Korea.
I know a mod answered this a year ago, but "되다" might be more intuitively understood as "changing" or "unfolding" (colloquially we say "to go," in all honesty).
So, something like "어떻게 됩니까?" ends up translated as "How are things going?" As in, "How does it seem things are unfolding for you?"
It's interesting to note that we don't use this colloquial phrasing in the case of age: it's not "He went old" but rather "He got old(er)"
For almost all cases I can think of though, you should be able to substitute it with that sense of "to go" (e.g., "the milk went bad," "my day went splendidly," or things like that).