Many thanks for the reply and link, Leo.
I see the ComReg page states, alright, that service providers are required to give 30 days' notice re changes to contracts, but it doesn't say what happens if the customer doesn't, for whatever reason, respond - it seems, based on Three's actions, that no response entitles them to bind those customers to the new conditions/prices.
I suppose this is similar to the whole argument about the auto renewal of contracts, I see there are moves in the UK to clamp down on them, I'm not sure about here. A pal of mine living in New York won a battle with an American newspaper over the auto renewal of her subscription with them, apparently New York law requires that the customer actually give verbal or written consent before a contract can be renewed, rather than the company going ahead and renewing it in the absence of a response. Hopefully we'll have similar here one day.
Meanwhile, I remain mystified by an agreed contract that has been significantly altered by a company remaining legal in the absence of the customer agreeing verbally or in writing to the changes. Surely ComReg should apply the same conditions in these circumstances as they do when the original contract is agreed - ie you can only enter in to it by agreeing over the phone or signing an actual or online form.
In my Googling, I found this on the RTE site (
https://www.rte.ie/news/money/consumer/2011/0516/138352-pulling-out-of-tv-phone-and-other-contracts/):
Is there any way out mid-contract?
Your best hope is that the mobile service provider themselves change a significant term of your contract, because then they have breached their contract with you and you can cancel.
No mention there of the 30 day notice business, just that the contract has been breached.
A legal minefield, I'd guess.