通常，这些呼叫按每一个呼叫计费，额外的信息部分附加给前转的呼叫。

Often these calls are billed per call with additional message units applied to the calls that are forwarded.

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它也向被叫用户提供了在呼叫激活阶段对剩余呼叫或对整个呼叫反向呼叫计费的方法。

It also provides the called user with the means to reverse call charging during the active phase of the call for either the rest of the call or for the entire call.

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许多移动电话运营公司都使用两档计费系统，分别对呼叫的每一档进行单独计费。

Many cell phone companies use a two-leg billing system that bills each leg of the call separately.

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