I got the same flyer the other day and I've just signed up this morning.
The lad came round showed me how it works, you plug in a little box to your phone line and they charge you for the calls.
You get the same deal as Utility Warehouse customers in BT land but you have to still pay KC line rental. I'm getting free calls to landlines and they've just started doing free calls to 0845 numbers but I've had to take their gas and electric, pay an extra £2 and you pay a £1.70 standing charge. I should save over £100 a quarter on my calls.
I did bend his ear over them not doing broadband in Hull.
Just got my first bill today
Call charges: £4.16 - they were all calls to mobiles, all other calls were free.
My monthly average amount KC was charging (not including line rental) was £28.
£23.84 each month is better in my pocket than KC's.