13. You had better keep your cell phone off when you go to bed.
你睡觉时最好把手机关了。
还能这样说：
I suggest turning your phone off when you sleep.
You should make your phone off while you have a sleep.
谚语：
Don't keep all your eggs in one basket.
勿孤注一掷。
14. I forgot to pay my phone yesterday.
我昨天忘了给手机交话费了。
还能这样说：
I omitted paying my phone bill yesterday.
I neglected to pay my phone yesterday.
谚语：
Elephants never forget.
象不忘事。
15. Your phone bill is due.
该交话费了。
还能这样说：
You have got a phone due to make.
You should hand over your phone fee.
应用解析：
due from 应收；
due to 由于、起因于，归功于；
become due 到期，满期
16. My cell phone is broken.
我的手机坏了。
还能这样说：
My cell phone doesn't work.
My mobile phone is out of order.
应用解析：
have a break 休息一会儿；
break from the past 和过去决裂；
break down 失败毁掉，拆除