How to activate a second hand iPhone 4S without the right sim card?

I bought this iPhone 4s from a guy without a sim card. I tried my fido sim inside n it shows no service. This is what shows on the screen when you turn it on '' No SIM Card Installed. Insert a valid SIM with no Pin lock to activate iPhone''. I don't know the correct carrier.

Does it fit perfectly or not? Because these days smartphones are often equipped with something called a Micro-Sim, Its smaller and thus taking up less size.

If that is not the case, Try to go to your local store and ask or they can detect what provider is owning it, If they manage to know, Try to get it locked free in a diffrent store (We call it here Sim lock vrij maken, Basically freeing your simlock.) But I'm not sure what in canada what stores do it, and wheter its legal or not. I really hope you can find a way to fix your issue.

Sounds like you bought a phone "locked" to a different carrier. You must get your phone "unlocked" to be able to use any mobile provide you want.

You need to learn more about mobile phones before you purchase then hope your phone will work on with your SIM card. Now you need to find a cheap way to "unlock" your iphone.

There are three kinds of SIM Cards: full size, Mini-SIM, and MicroSIM, distinguished by their size. The iPhone 4 uses the MicroSIM format. Yes, you can convert mini-SIM cards to work with the iPhone 4, allowing you bring your existing service and phone number from another phone company to the iPhone. This process requires cutting the mini-SIM down to the size of the microSIM. There are some tools available to ease this process (compare prices on these tools). This is only recommended for a tech savvy and those willing to take the risk of ruining their existing SIM card and rendering it unusable.
It is the first item on this list at this safe ABOUT.COM website.http://about.pricegrabber.com/search.php?form_keyword=microsim&mode=about_ipod.