After nearly 20 years with zen (my adsl username was firstnamelastname@zen) I switched to plusnet fttc on a contract term that halved my bill. I also paid upfront for 18 months of line rental.
However, after 6 months I really wanted to expand my public ip range and asked how to get at /29 allocation. Not available on the consumer product, but I could change to the business product line - not as painless as you'd imagine, I had to be allocated a new dsl username as the old name was going to be cancelled. I could keep the existing phone number (doesn't get used) and had to be issued with a new (identical) home hub thingy. All the billing was changed to my ltd. co.
Everything went well, I was assigned a /29, I paid £20ish for the home hub and was refunded the balance of my upfront phone line payment. So I was £20 down on the hub and £100 up on the line rental.
My next bill is Feb 9th 2019 - I have a DD in place that they've never drawn against, there is an undertaking on the forums that everyone will only be charged 90 days worth of fees once they get the billing fixed. As it stands today I'm 6 months into the new contract and have paid £20.
Any accountants out there want to tell me how much I should be accruing against the inevitable invoice which at this stage looks likely to arrive in the next financial year .....?