Honestly it just depends on the definition of invalid, it's still giving you information on where you need to go so it still gives you more information than when you started it's not like it just leaves you to a dead end number, now what some other people were proposing which is a virtual number and then just toss the phone after that I don't agree with. Nor do I agree with a number that doesn't give any info aside from just hanging up or endlessly ringing