That is not entirely true. Some "World Phone's" at Telus like the Storm and the 8830, allow the use of SIM cards, which is what Rogers uses on their GSM network. Take the Sim card with you to the Telus store and ask to try it in the unlocked World Phone, they may need to make a quick call to allow the feature to be enabled by their network, but the phone itself is entirely capable, I use my storm everywhere in the world on GSM networks, even though I have a Telus contract here in Canada.
Good Luck