Just wondering what the options for cancelling a Fibre contract are before installation? My elderly parent have been talked into switching to Fibre by a door to door salesman and the "deal" looks pretty rubbish.

Sure it looks very slightly better than their current ADSL, but only because they've been way overpaying for that for years...  they agreed to it 7 or 8 days ago but only got the confirmation email today - prompting them to let me know and yeah it just looks like a crap deal, especially since multiple providers are offering 3 months free or 6 months half price, etc

They have not had it installed yet but rang me slightly stressed because they're now outside some 5 day cancellation period, but given it's not even installed yet can they cancel without any penalty?

(Does not matter which company at this stage as I said they should ring them and try to get a better deal or cancel it first, so want to give said company a chance before naming...)