gwd.sec 9 , 3

这个是E

HAS PLUMMETED没问题 习惯用法 后接 IN THE LAST YEAR

这里的WHILE有尽管的意思也有一段时间的意思 表明现在的人尽管有价格下降和手机普及的因素，当电话公司的包月费很便宜的时候 人们还是舍不得白天用！

with不一定要表达一个点吧，也可以是一种状态：

14
because of a situation that exists

With John away there's more room in the house.
with something doing something
I can't do my homework with all this noise going on.

12
used to say what position or state someone or something is in, or what is happening, when someone does something

She stood with her back to me. We lay in bed with the window open.

She was knitting, with the television on.
with somebody/something doing something

We jumped into the water with bullets whizzing past our ears

--from LDOCE

如果这样，当电话公司报月费很便宜就应该提前作为并列的三个让步条件之一：1，价格下降 2，手记普及，3，包月费便宜。而这时候provide unlimited airtime还是要在后面分句里面作为在周末和晚上用的状语。

（尽管//伴随）无限服务的成本降低和移动电话的普及，当许多无线公司以很少的月租费提供无限制的白天服务，许多人还只在晚上和周末用移动电话（言下之意：移动电话白天使用也足够便宜了，人们却不用）

不知道原句里哪里说了无限制的白天服务, 看了半天就看到了无限制的通话时间。而且when numerous wireless companies provide unlimited....已经说得很明白了只提供晚上和周末的无限制通话时间。