deactivate sim by mistake, can i re-enable it ?

Hi
yes you can reactivate the plan yourself. This is the procedure.

How to reactivate your Fizz account when you have a SIM card:

1- Go to the Reactivate page and log into your account.
2- Review or adjust your plan details and click Confirm.
3- Verify your phone number (if you are reactivating within 60 days) or select a new phone number. Learn more about changing your phone number
4- Review your addresses and plan details, then click Submit.
5- You go to the payment interface to pay for the first month of your new plan.

Source: https://fizz.ca/en/faq/reactivate

If you would like to contact Fizz, you can Live chat with support from 8 AM to 9 PM every day:

1- Connect to your Fizz account by clicking « Login » in the top right corner at fizz.ca
2- Any ad blockers in your browser should be disabled.
3- Click on one of the help links from the Solution Hub, like this one: https://fizz.ca/en/faq/reactivate
4- The green chat bubble should appear after a few seconds in the bottom right corner.

If the chat bubble does not appear, this means that the number of sessions waiting for our answers surpasses our processing capacity. If that happens, send us a private message via Facebook Messenger or Twitter.

Hi Francesco,
If you still are not able to reactivate your sim card, contact Fizz for support, I am sure they can help.
To do so, first log into your Fizz account.
Make your way to the Solution Hub.
On the help page pertaining to your issue, click on the chat bubble located in the lower right-hand corner.
The chat service is available every day from 8 a.m. to 9 p.m. EST. The chat bubble won’t appear outside of these business hours.

You can ask fizz on the live chat through the website, facebook messenger or twitter. They are usually there 24/7 on social media. They will be glad to help you!