Welcome to the community!
Sorry to hear you've incurred unexpected charges. Firstly, you should note the 1000 International minutes is a promotional offer and not a part of any plan details. If the duration of the promotion was not outlined when it was received, it's end-date would have been provided in your bill a couple of months prior to its actual termination. Is it possible your promotion has ended?
Are you aware that those promotional minutes only apply to calls to certain Countries? You can view the included Countries here. Were your calls made to the included Countries?
It should also be noted that all calls using mobile services incur Airtime charges plus long-distance charges, if applicable. Those 1000 International minutes are only for the long-distance portion of calls. That is, airtime charges would still apply. If you have a plan with a limited number of airtime calling minutes, excess airtime usage would incur additional costs -- even though there may be available International minutes remaining. For example, if you had a plan with 500 Canada-wide minutes (airtime minutes), making 600 minutes of calls to Countries included in those 1000 International minutes would require an excess usage of 100 airtime minutes. Does your plan include a limited or unlimited number of Canada-wide minutes?
I understand this is a difficult time and receiving such a bill even more distressing. If you're unable to make full payment on the bill, you might consider arranging a payment schedule. To make an arrangement, you'll need to contact the credit operations team. It should be mentioned that a payment arrangement might not be available in all situations.
You should note this forum is community-driven and not intended as a venue for customer services. If you would like to further discuss your situation, you would need to contact customer service. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above.
Hope this helps 😀