Does anyone know whether I can use the same Treo with a subscription to Cingular's data network and use Roger's (Canada) for my voice on the same phone?
If yes, what's the best order of subscribing? The phone is less expensive through Cingular, so I'd like to get it that way if possible.

Why would I want to do this? Data is cheaper with Cingular, even if I use it in Canada occasionally. But Roger's has a US/Canada calling plan with no roaming charges, something that Cingular doesn't have anymore. And work requires use of the Treo if I want a connection to the email servers there.