Someone is telling you incorrect information. Rogers has changed their requirements regarding the iPhones subsidized through the carrier which are now requiring all Smartphones which includes the iPhone 3GS to have an eligible voice and data plan on 36 month term. When the iPhone 3G was launched a year ago it was first allowed to be sold on term without getting a data plan. Rogers later changed this due to an inability to recover revenue on the subsidized hardware fast enough before the customer wanted to upgrade again 12 months later (12 months between upgrades was the old eligibility). Their new upgrade eligibility of waiting 24 months between upgrades is understandable from a business standpoint since customers like changing hardware before they have finished their 36 month term commitment for the first phone. When you get an iPhone subsidized through the carrier it's heavily subsidized based on term renewal and the cx subscribing to an eligible voice and data plan with a higher monthly service fee than a customer that doesn't use a Smartphone. The only time you wouldn't need to get a data plan is if you're buying the iPhone 3GS at full price with no term renewal. Though if you use it on your account without an eligible data plan then you're also fully responsible for any data charges you incur.
http://www.rogers.com/web/content/wireless-products/iphonefaqs?setLanguage=en&cm_sp=Consumer-_-Wireless_iPhone3Gs_0609_Eng-_-3GsPrelaunchLowerBadge
ROGERS UPGRADE ELIGIBILITY: For those that already have a Smartphone (iPhone 3G, HTC Diamond/Magic/Dream/Touch, Palm Treo, Blackberry, etc) subsidized through Rogers they also changed their upgrade eligibility several months back to only allow upgrades to another Smartphone such as the iPhone 3GS every 24 months. So if you got your iPhone 3G in July 11, 2008 then you won't be eligible for an upgrade to any Smartphone including the iPhone 3GS till July 11, 2010. When the iPhone 3GS is launched June 19, 2009 you'll be able to buy the iPhone 3GS at full price unlike the first iPhone 3G when launched did not allow buying it at full price on no term renewal.
