You can if you'll be out of the country for a month or more, you will be charged $10 a month for the time gone. It's a seasonal hold and can only be done for a maximum of 6 months. You can call customer service to have them place your account on a seasonal hold.
If you will be leaving Canada, you can put the account on seasonal hold @ $10/month for 1-6 months. If your plan is no longer available, you will need to choose one of the currently available plans when you resume service. If you're still interested in switching, you will need to call customer service, as only they can place an account on seasonal hold (no charge for this). You can resume service by simply switching to a new plan through self serve.