It hasn't failed me yet, but I don't make too many 08 calls anyway.
If I took the tickle (there's a phrase I never thought I'd type) then I, through VM, would be condoning the scourge that is the 08 rip-off. Using the sayno... site means the company I'm calling don't make anything out of me (I think) especially if there's a freephone alternative.
It probably doesn't work like that but just let me have my dillusion that I'm screwing them for a change instead of the other way 'round.