Economy 7 is controlled (surprisingly enough) by a timeswitch. In older installations, this was a seperate mechanical electric clock/switch, and in newer ones (in the UK all by now) it is integrated into the digital electricity meter.
Either way, it is set (adjusted) only by the Electicity Board that owns it. The time that the 'economy' rate is active is controlled soley via this timeswitch and when active, charging is routed to the appropriate meter.
So, if it's active during the day, it points to a defective or mis-set timeswitch (which you can't change.) Now, if you only use it for the dishwasher etc, then being on during the day is a benefit (the charge is according to the relevant meter), but if it's for storage heaters, you really want to get it changed so it all works as intended. Up to you; it's not your fault.