【俚语】

Bars n. 条
a bar of soap
一块肥皂
a chocolate bar
一条巧克力棒

【例句】

I have no bars on my cellphone.
我手机没信号。
I only have one bar on my cellphone.
我手机只有一格信号。

Signal 信号

【例句】

I have no signal on my cellphone.
我手机没信号。

Reception n. 信号接收效果

【例句】

The phone reception is really bad in the mountain.
电话信号在山里真的是特别差。

No service 没信号

【例句】

Suddenly I’ve got no service on my cellphone.
我手机突然没信号了。

Not in service 停机/不在服务区

【例句】

Sorry. The number you have dialed is not in service.
抱歉，您拨打的电话已停机。