@panicos "I was smart not to set up a direct debit with pipex".
Probably not, as the only other way is Credit Card. You can cancel a Direct Debit but you cannot cancel a Credit Card agreement.
@sezzica "my polite letter stating my direct debit had been cancelled". I presume you cancelled it with bank? Pipex have been known to set up again DDs that have been cancelled. This is not allowed under the DD rules without your consent. Keep an eye on your account.
Anybody with Direct Debit suffering from unexpected payments they weren't given 10 days notice of or payments after the DD has been cancelled can demand immediate repayment from their bank under the DD rules. Individual bank staff might argue, but there is no way they can refuse. The bank then has to reclaim it's money from Pipex's bank. If enough people do this, then Pipex's bank might ask a few awkward questions.
Just cancelling your DD to avoid paying is not wise though as it could affect your credit rating and Pipex use debt collection agencies. You could however write to Pipex HQ (Recorded Delivery) saying that you have cancelled your DD but will pay anything genuinely outstanding by cheque on receipt of a final invoice.
On general complaints, ISPA appears to be the most effective. Pipex Communications is a member, so that covers both Pipex Internet and Pipex Homecall customers.
CISAS will only look at a case after 3 months, unless your ISP has agreed arbitration and provided a release code.
OFCOM will nod their head sympathetically and file your complaint to see if a trend builds up.