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If you print/save your invoice details you will see exactly what you are billed for, if you did go over the 1000 minutes for the specific countries that it is free for then the charge would be valid. To learn how to print/save your invoice see here.
With that being said since it is a large amount and if you are unable to pay it in full you can set up a payment arrangement with Fido. You will have to reach out to the credit department, you can get that info here.