Cell phone contract? (Toronto)

Hello!

I just wanted to ask if somebody can tell me what possibilities for cellphone-contracts are offered?
I ve heard that usually contracts with very high monthly fees and a commitment of Protected content are offered from the provider?! I would just need a cell for 4 months for my exchange semester in Toronto, so I thought of a prepaid card? That should work, too, right? Will I get a prepaid card at any store with electrical equipment to put in in a activated cell phone that I already have?

or maybe somebody wants to get rid of his/her old contract that I could take over (so that I pay the rest of the months till the contract expires)?

Thanks a lot!!
bye bye
Nicole