I don't know what Uk Telco customer service is like but here is our saga with Orange here in Spain.
Took out a contract for unlimited monthly access to the Internet via a dongle. It works OK but loses bandwidth at peak periods and in bad weather. Got this months bill for 249 euros. Somehow they have changed the charging to per minute from the fixed fee.
looked on the Internet for a customer service number. None except one for Orange mobile phone customers. No probs I will call in at one of their shops. Hands in air, yet another customer with this problem. Let me take a copy of your bill and we will try and sort it. Puts copy on pile of other similar bills and goes back to polishing nails.
Meanwhile company take money from bank account as they are allowed to do, despite us asking the bank not to pay any more than the standard monthly amount. What about getting our money back off Orange? ........................mmm best to ask Orange for it.
Back to shop, Have you sorted it yet? No will let you know when it is sorted. What about our money? Don't worry. Hispanic shrug.
Some days later back home, still not sorted. Decide to write a letter to "Head Office Madrid Customer Service". No address for such a dept or indeed an office. Not unusual in Spain at all. Have since obtained a fax number but haven't got a fax!
Only recourse is the usually brilliant Shop complaints form. All shops have them and if you complain then the Police get involved. Most sort things before it gets to that stage.