O2 Back in the day.
Wen with O2 back in the day and their "30 day money back happiness guarantee". I kinda knew they had 2 products. A direct one, which was amazing. And a reselling BT ADSL which was massively over subscribed (congestion and slow connections).
It crawled and crashed at 5pm every day. So I complained. They sent a new router. I played along. They gave loads of excuses... got up to the higher customer support engineer, was told "we are sure to fix it later, in about 1 months time", me being savvy, said "sorry, it just dies in the evenings, probably congestion, you need to buy more service off of BT", and to my suprise the engineer agreed. "I game on my Xbox, and get the same problem" he said... but then reverted back to the "script" saying it must be me/my router/etc. ;)
So after 29 days, I got my refund, moved to another supplier, oh and did not have to pay a connection fee a setup fee or cancellation (I technically made a profit, as the setup fee for an old connection is generally needed when re-installing the line).
But I guess, the other 1000s of customers... those I feel sorry for.