BT.
I'm currently contemplating upgrading to fibre broadband but I'm reluctant as I've seen many horror stories of orders going wrong and people being without the internet for weeks. I need the internet for my work (before you ask, porn star, I can lick me own tits and everything). I've tried upgrading 2 times before, they keep delivering the equipment to the wrong address.
Also, the HMRC, they owed me some money on my VAT return last year, I must of spent hours on the phone, going round and round in circles. Enough to drive anyone mad.
Any large organisation, especially government run ones, are fucking useless.