The reason I'm with PN ?
My Gran had a problem with her BT line, I called BT, I spent two days going round in circles with the Indian call centre trying to explain the cadence ring was a solid tone on her line which was messing up her emergency call equipment. They constantly blamed her equipment until I removed the master socket, hooked up a digital storage oscilloscope to the line and offered to email them the waveform at which point I managed to be transferred to a UK engineer. A week later, the line was fixed.
When I had an issue with my line just after joining PN, I could make calls but couldn't receive incoming calls. I called the PN faults line on a Saturday morning, got through in 2 minutes, had the fault logged within 5 minutes.
Don't get me started on TalkTalk and the issues I've had dealing with them on behalf of customers ! One of my neighbours had to use my connection for over a week while they sorted out her problem (failed card at the exchange but they blamed her computer having a virus, then her router, then my brand new router, then my Linux laptop for having a virus, then her telephone etc etc).