I think the chances of any case being brought against you because you mixed up the numbers on your credit card a bit are pretty slim. If they were to bother, they would have to prove you did it on purpose.
I normally just get a standard response saying the card number was not recognised and if I wish to continue my subscription, to follow a link where I can update my payment details.
I can't really see the danger in it.
Anyway I don't beleive that this would come under obtaining a pecuniary advantage by deception. The following are the four definitions:
(i) Being allowed to borrow by way of overdraft, eg where D pays for goods or services by way of a cheque drawn on his own account having been instructed by his bank not to do so, he will commit an offence under s16 if the cheque is supported by his cheque guarantee card and the bank, as a result, has to debit the amount of the cheque from D's account, thus increasing his overdraft.
(ii) Taking out a policy of insurance or annuity contract, or obtaining an improvement of the terms on which the defendant is allowed to do so, eg where D secures a policy, or a policy on better terms, by falsely stating that he is a non-smoker where this is material to the issue of the policy or its terms.
(iii) Being given an opportunity to earn remuneration or greater remuneration in an office or employment, eg where D lies about his qualifications and secures a job as a result, the job is the pecuniary advantage obtained by deception.
(iv) Being given the opportunity to win money by betting, eg where D by deception is allowed to bet on credit or cash terms.
