Ovo tells my 95-year-old mother she owes £31,554

When SSE became part of Ovo, the account was switched and the old reading incorrectly input. Photograph: Sam Oaksey/Alamy

At 95, my mother has never switched electricity supplier, and we were not expecting much to change when her account moved over from SSE to Ovo.

She has lived in the same small bungalow since 1949, and when I received an email in August about the changeover, I followed the instructions and created an online account. But when I logged in, it showed she owed £31,554.