Cancelled isn't cancelled until they say so in writing

A woman's husband had a stroke seven years ago and hasn't been able to use his phone since. She says the account was closed. The billing carried on anyway. This is the among the most common complaint I get. You phone, someone says they'll cancel it, and nobody does. Months or years later you're still paying, and getting the money back is very hard, because the company says it has no record of your request. So, cancel in writing, by email, keep the sent copy, and insist on written confirmation with a date on it.
Then watch your bank statement for the next month or two to check whether the debit order has actually stopped.