I would suggest you cancel your direct debit as soon as possible. This will get their attention immediately and, this is from direct experience of the same matter, someone will either call you very soon or send you an email advising you of all the horrible (joke) things that will happen to you if you don't pay your Bill. Explain to them what you are going to do ie wait for your Statement and pay the full amount owing for that month. they will still try to persuade you otherwise but stand your ground. The only downside of this is maybe you are on a cheaper tariff because you pay by direct debit, which may go up if you stop. Check carefully this is not the case.