Hello Amandabaey,
Welcome to the community!
Toll free numbers simply means that there are no long distance charges associated with the calls. Airtime will always apply when calling any toll free numbers (see here). It's the same with any of the mobile providers. The only way to not incur airtime charges is to call them from landlines.
You should also be aware that some toll free numbers may include long distance charges when you are roaming outside of Canada (not included in Fido Roam or Travel packs) (see full details here and here).
You will be charged for any calls you make or receive since the plan does not include any call minutes or SMS/MMS. The rates are $1 per minute for your calls and Long Distance (LD) calling at 45¢ per minute within Canada (see here).
Additionally, you will not incur any extra charges when you receive text messages. However, sending SMS costs 25¢ per message sent from Canada to a Canadian wireless number or 45¢ per message sent from Canada to a US or international wireless carrier (see here).
Sending MMS to a Canadian wireless customer costs 50¢, while to a US or International wireless customer cost 75¢ (see here). Again, you will not incur any extra charges when receiving MMS while in Canada. Note however, roaming data charges would apply when outside of Canada.
Hope this helps 
Cheers
