Email infromed me I paid money which I never did!

[hanasime]

Hello,

today I recieved mail from paypal that I paid 6.87 GBP to a merchant Parcel Monkey Ltd. I never paid for this!!!

Should I just regard this as a spam or investigate how is it possible that someone is using my email address telling me that I paid for something which I never did?

[crazykat]

hi there

on the 29th of feb i recieved an email reciept from paypal saying i have paid 6.50 usd to 

facebook ireland ltd which i  never did!

why would someone say this and why?