Only thing is that mistakes usually allow the party who made them to void the contract. Don't want to turn up to the game against Wigan and be faced with 'Computer says no'.
If they void your season ticket over £25 from a mistake they made, that's incredibly petty and they don't deserve your support.
I'd keep hold of it until after the start of the season (so you know your card works) and if there's no problem spend it in the Saints shop so the club get it back ........and you get some nice clobber!