British telecom, when their customer services was in India. They actually drove me to cry, tears of frustration, honestly.
My Wi-fi went down, after ducking about for four hours, yes four hours, testing the line and making me hold on whilst they did it, they sent an engineer to the house. Engineers said the problem was at the junction box.
Apparently engineer reports don't get actioned, no one reads them. So when I called two weeks later to find out what was happening, yup, they tested the line for another four hours.
It went on daily, I even have w copy of the transcript when I chatted them once and the rep said, "I don't know what to do, can you help me".
Eventually they made an appt for the second level engineers to come out, but the Wi-fi had been down for a month and it was another three weeks, so I sent a complaint in.
Lady phoned me from complaints, I explained the issue, said three weeks more wasn't ok, she said no problem, she agreed, she'd find a quicker time slot. She gave me one in a weeks time.
She then phoned me ten mins later saying she'd released my old one, and hadn't booked the new one in time, so the slot was gone, and she could only now get one in five weeks,
So yes, I complained after daily calls and chats for a month, many days spending four hours a day on the line as they tested it, becayse apparently they had to do it every time, I complained that I had to wait three weeks, and they made it five instead,
And to had insult to injury, I said I want compensation for this, at least what I've paid for the service I haven't received and the complaints lady said, sorry I don't deal with that.
Absolutely awful.