So the question really is , was your cancellation instruction ( to not bother with ADSL/FTTC ) , given to BT in sufficient time so it should have no effect on the landline existing service, but BT never actioned your cancellation request quickly enough ( evidence of this would be if you still received a new BT router after you thought your order was cancelled ) or you never actually made that cancellation request as quickly as you state , a much more unlikely scenario is , somehow your request to cancel your broadband order taken to mean cancel your service entirely , and that may be down to semantics , the difference between saying ‘cancel my order for broadband service ’ or ‘ cancel my service’, especially if ( for arguments sake ) your reason for the call was ‘I don’t want DV telephone line ’ was interpreted as ‘ I don’t want a telephone line ‘, I dare say we will never know the exact conversation.
In a way it’s irrelevant, if your landline service is now ceased , the fact the copper wire was never removed isn’t the issue , the exchange PSTN equipment that delivered dialtone was ‘switched off’ and there is no way to issue an order to get it switched back on , because that equipment is ‘retired’ and it’s not allowed to be used for new customers, which is what you now would be , a new customer.