Welcome to the community!
Sorry to hear that you lost your phone, did you try calling it to see if anyone would answer?
Is it an Apple or Android phone? If its an Apple phone do you have the find my iPhone app installed and activated? If you do have in enabled you can trying using to see if you can located the phone you can get more info here.
If you have an Android phone and have find my device turned on you can also try locating your device through Google you can get more info here.
If you are not sure if you had those features turned on you can still try locating the device in the event it was activated.
You can also report the device lost to Fido and they can blacklist the device so it will not be able to work on any carrier in North America. If you will try to locate the device though you should not have the phone blacklisted or disconnect your service just as yet because you will still need the phone to be active in order to locate it. You can have Fido block all out going calls so no one can use it to make calls.
I am sorry to hear about your phone. I can understand this situation is less than ideal for you. That said, we can definitely help you place some restrictions on your account, until hopefully you can find your phone.
I'll send you a PM shortly so we can look into this together.
Block the phone so no one can use it untill i am able to contact the movie theatre to determine if they found it. If they do find it I will contact you to reinstate the number for me.