Re: BT tricked me
"In the Reg yesterday I learned that Caller ID is built-in to modern telephony. "
Not just caller ID.
ALL the "added value services" are just functions in the telephony switch. There's no cost to the provider for enabling them other than the labour cost of someone doing so (if they were enabled by default they wouldn't cost a thing)
It's the same scam as charging monthly rental on a telephone which cost £5 or less to procure and supply.