Do I void manufacturer's warranty if I unlock my iPhone 5 from my Canadian carrier?

Hi

I am looking at signing onto a contract or tab for an iPhone 5, in Canada, using one of the local providers (Rogers, Telus, Bell, Virgin etc). I was told in one store that obtaining an iPhone 5 on this basis will mean it is locked to the network and that all the networks here are unable to unlock them. I could do it through a third party but that would void my manufacturer's warranty (ie AppleCare).

The Apple store here in Calgary told me different - they said that phones are easily unlocked for a fee by carriers, and didn't mention any loss of warranty. I have previously unlocked a phone through iTunes in Australia, and have had the same phone serviced by Apple with no problems at all.

Could someone please clarify what is really the case here in Canada?

Thanks