Welcome to the community!
The mos refers to months. So your plan would have the 1000 International minutes for 24 months (or 2 years). You should note that those minutes are only applicable to certain Countries. You can view a list of the eligible Countries here. Is it possible you made the calls to destinations which are not included in the 1000 International minutes?
Hope this helps 😀
One other thing to consider is that those 1000 International minutes are only for the long-distance (LD) portion of the calls. All calls are charged airtime plus LD, if applicable. With those 1000 minutes, your calls to one of those destinations would be charged airtime. Do you have a plan with a limited amount of call minutes? If you do, you might have been charged for additional call minute usage rather than LD. For example, if your plan had 500 included Canada-wide minutes, making 600 calls to one of the included Countries would mean that you would have used an additional 100 call minutes and charged accordingly. You would not have been charged the LD portion because you are still within your International minute allotment. However, your airtime or call minute allotment would have been exceeded.
Have you had a chance to view the billing details? You should be able to do so via My Account --> Billings & Payment --> View Bill. From there you can Save or Print a PDF copy of your bill. You can also view the detailed billing online by clicking Other charges and credits.
If you still notice some discrepancies, you would need to contact customer service so they can investigate your account. Alternatively, you might consider sending @FidoSolutions a PM. Once they verify some information, they will also be able to access your account. 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 😀