China Telecom is one of the biggest service providers here in China.

　　中国电信是国内最大的运营商之一。

　　SIM card 手机卡

　　There's no SIM card in your phone and that's why you can't use the mobile internet.

　　你手机里没有sim卡，这就是为什么你不能上网的原因。

　　Service plan服务计划；套餐

　　Some handsets are free when you sign up to certain service plans.

　　当你签约一些套餐的时候，有些手机就是免费的。

　　roam /ro?m/ v. 漫游

　　On my vacation I didn’t realize that my phone was roaming. I paid a lot of money for each call.

　　度假时我没意识到手机是在漫游，所以每个电话都花了好多钱。

　　coverage (信号)覆盖

　　Which service provider has a better coverage, China Telecom or China Mobile?

　　哪个运营商的信号更好呢，中国电信还是中国移动？

　　top up 充值

　　I need to go to the shop and top up my mobile phone.

　　我得去商店给我的手机充下值。

　　out of data/minutes 没流量了/没话费了

　　I am out of data.