How much does it cost to factory unlock an iPhone 4?

<Edited by Host>

Bell are the only ones who can tell you this. All the phone companies are different and only Bell can tell you this and they are the only ones who can unlock your phone for you. Contact them and ask them if they will unlock your phone for you and if they will do it for free.

Bell does not offer unlocking. Sell it and buy a phone you use.