How is FREE Fibre implemented on the account/bill?

[#1]

I’m considering an 18 month contract. The online order shows:

Monthly costs

Unlimited Fibre FREE (Free every month for 18 months, then £18.56 thereafter)

Monthly Line Rental £22.99 (£22.99 every month for 18 months, then £23.19 thereafter)

Caller Display FREE 

etc....

How is this shown on the account/bill? Is it shown as below which seems to match the PN CPI Guide

Unlimited Fibre	£0.00
Line Rental:	£22.99
Total	£22.99

Or perhaps it shown as below - by using a discount for 18 months?

Unlimited Fibre	£18.56
Special offer discount	-£18.56
Line Rental:	£22.99
Total	£22.99

For the March CPI + 3.9% increase, let’s say it is 20% for this discussion, the ongoing price could be:

Unlimited Fibre	£0.00
Line Rental:	£27.59
Total	£27.59

Or if the Fibre is discounted, perhaps the "special offer discount" isn’t increase with CPI?

Unlimited Fibre	£22.27
Special offer discount - no change in this due to CPI	-£18.56
Line Rental:	£27.59
Total	£31.30

I'm trying to understand what the potential costs could be.

[#2]

AFAIK it is shown on the bill as a discount. However , the discount is also adjusted, so that the nett cost is effectively increased by the CPI increase

[#3]

Thanks @MisterW 

My current provider shows a combined total for my broadband package (Fibre + LR) and then applies a "special offer discount". The discount wasn't increased last March hence my question. 

Do others concur with @MisterW ?

Perhaps the PN CPI guide should show an example with a discount making it FREE? 

[#4 · Accepted solution]

@BarkingMad for information, it was confirmed by PlusNet staff in this thread https://community.plus.net/t5/My-Account-Billing/Question-Annual-CPI-increase-for-contracts-rectifie...

[#5]

@MisterW 

Excellent. I'd searched for CPI in the forums and hadn't seen it in the drop down window of results - it was at the bottom and I needed to scroll down 😞

It also makes logical sense - if something is FREE - how can it be affected by a CPI increase.

Thanks again.