is it possible to upgrade my phone to lets say the new blackberry curve 8320. and then switch back to my old phone(or get the iphone immediately after) and sell said blackberry?

or is there some rule where i must activate said phone and keep it for a while?

 

you should be able to sell it without any issues. you might have to activate it initially but i'm not sure about that.

 

you can do whatever you want with the phone.

 

No rule. You can do whatever you want with the new phone. Though someone might want to chime in about the iPhone. I think there are special circumstances when getting one like a different SIM or at least a specific data plan.

I did it with a Z520 with cingular. I bought it and sold it the next day as I'd rather use an unbranded, unlocked phone to go with that plan.

 

Blackberry >>>>>iPhone

 

i prefer iphone's internet browsing over blackberry

 

What i do is when i get a new phone i use the insurance plan on my old phone to get a new one. I then sell the new one and use my new every 2 2 weeks later