Economy 7 supply – suddenly extended hours?

Hi there
For about ten days the Economy 7 supply to our storage heaters has remained live (on) well past the usual hours: daily 'til 9.40am – and today (Sunday) even until 10.15am. Is this a meter/supply fault? I don’t want to be charged for unrequested usage – even if it is at a ‘cheaper’ rate.
I have tried contacting Bulb on the telephone over the last week on several occasions, but after 20mins without reply every time – I have given up. Help please!