Well, Peter, I for one am not a "banking novice". And I have more than once got money back from a bank after funds were taken wrongly against a direct debit mandate.
In any case, don't take my word for it - I referred to just two articles, but there are plenty more on the Web. What evidence can you offer to support your case?
Sure, as you say, charges can only be made against a card up to the credit limit (although in practice credit limits are often exceeded), but I have a £15,000 limit on my main card and don't want £15,000 of incorrect phone charges on there. Whether or not with a single transaction, it would take a lot less than £15,000 to clear out my bank account!
And, yes, card companies will investigate complaints, but the onus is on the cardholder to prove that the charges were incorrect. Contrast that with cancelling a DD, which most of us can do online in a matter of seconds.
Even cancelling your card, a drastic step, does not stop a retailer taking funds against a continuous authority. The card issuer will then pursue you for payment. When you cancel a DD (NB just the DD, not the account), no more funds can be taken.
Here is a quote from BBC Moneybox:
"Everything was fine until he tried to cancel. He called the retailer - that did not work, so he called the card company. "They said they could not do it without the supplier instructing them that they would not be taking any more direct debits," he said. Robert decided to cancel his card but his account with the card company carried on, so the debts kept piling up."
Read the whole article at:
http://tinyurl.com/38vf6 Sorry, Peter, but, based on extensive and widely published evidence, you are wrong on this.