The Enigmatic Telephone Bill (3) - What is a Tier discount?

In my series of posts on the Enigmatic Telephone Bill I am talking about the complexity of price plans and services, explaining various discounts that are used by telephone companies and showing how easy it is for the telephone companies to miscalculate your bill.

In My previous post, I talked about a Tier discount rate plan I have.
This post is about Tier Discount. This type of discount is a type of Volume Discount, which is based on the volume of your usage.

Here is how it works:
If you talk up to 100 minutes a month, your rate, let's say is 0.4$ a minute.
If you talk more than 100 minutes, but up to 200, your rate is 0.35$ a minute.
If you talk more than 200 minutes, but up to 400, your rate is 0.28$ a minute.
If you talk more than 400 minutes, your rate is 0.25$ a minute.
This type of discount "encourages" you to talk more.

When the monthly bill is calculated, the Billing system collects all the relevant calls.
In many cases not all the calls are included in this discount.
For example, if you have a family & friends plan, the calls in this plan may not be included in the Tier discount.
Then the total minutes of the relevant calls is calculated against the tiers.
If you follow your bill during the month, you see the calls rated with the basic rate which does not show the Tier discount.

I hope this is helpful.