When I was self employed, a customer called me out to a cut cable. Turned out they were having a driveway relayed and the contractor had chopped through Virgin's cable which was a couple of inches below the surface.
Virgin wanted to charge the customer 100s to relay the cable and were having a right ding-dong on the phone with him about it. And it turned out this guy worked for them!
For what it was worth I got on the phone to them and told them their work did not comply with regulations, but they were not budging.
A slightly different story, but in the early days (November 1999) I was with Orange on contract, it had just ended and I wanted to port my number to PAYG.
She wanted to know why I wanted to swap to PAYG. Now, for all she knew, it might have been some personal reason such as divorce or bankruptcy (it wasn't), and I told her as much and that I would not divulge the reason and in any case, that would not stop her from porting my number across to PAYG. It wasn't as if I was asking to leave Orange altogether.
She flatly refused. So I stated that I hoped the call was being recorded (companies had just started doing that) and said that it sounded very like she was desperately hoping that by threatening me with the loss of my number, I would stay with Orange and renew the contract, but that it had horribly backfired and guess what? I had made the decision there and then to ditch the number and was going to move to the newly formed Virgin Mobile (funny, given the previous story!), who was the first MVNO.
I've still got the same number now.