Hey joellemondou!
Although this thread is quite old, I'd like to add a little more information since I came across it. Since you did mentioned that you called Fido to declare that the phone was lost or stolen, then a service restriction was put in the account so no usage can be done to avoid a high and expensive bill. If your new SIM card was activated under the same number you had from the phone that was stolen then you will have to contact Support or Live Chat to have the restriction removed and to double check if your SIM card was activated.
But if you did cancelled the number from the phone that was lost or stolen and activated your new phone under a new phone number then I suggest you to contact your original point of purchase of the IPhone so to make sure all was done correctly. Also you can subscribe to Fido's Device Protection as part of your Fido package so to be covered if the same were to happen again. You will be able to replace the phone at a minimal fee, click on the Link below to verify the replacement fee for the any and all phones.
http://www.phoneclaim.com/fido/program
Hope this helps!
