Scottish Power in the dark about my mother’s electricity supply

Energy firm confirmed it had closed my mum’s account but then asked for meter readings and sent her a bill for £1,979I manage my elderly mother’s financial affairs. I noticed over a year ago that there was no sign of electricity payments on her bank statements, despite the fact she had a dual-fuel contract with E.ON. E.ON told me that her electricity account had been closed. I discovered that Scottish Power was the most recent supplier so contacted customer services, to be told