Face time charges/short code txt

So can anyone tell me why Apple is charging customers when using FaceTime? I recently noticed on a cell phone bill that I had extra charges when travelling in the US. It turns out these extra charges are from using FaceTime, even over Wifi, and they are called TXT MSG Short Code Programs .

This seems quite unfair, that Apple would charge only Canadian Customers, but if you are a US customer, even while travelling abroad and using FaceTime, Apple will not charge you. What is the real reason for this charge? And why are Canadian customers charged, but not American?? Very unfair and confusing.