Little girl in big city

I always feel so small town girl when walking through Amsterdam.
It was dark and thank God there was someone with me while walking from Duivendracht to the HMH. But I figured I could get robbed, raped or ripped to peaces anyhow.
It was not until the next morning I noticed the signes that said:
Do not call. If you make a phone call, there are people around here, that will steal you phone, by just running by and grabbing it from your hand.
Well, that was reassuring.
If your fucking Amsterdam police, do your job, instead of posting signes that scare the hell out of me.