Can i keep my current internet provider until Fizz is activated at my address ?

Hi Hoang

Yes you can do

This is from the guide

Avoid doubling up.

Once your Home Internet plan is activated, don’t forget to contact your previous provider to cancel your Internet subscription with them, and avoid paying double.

Source: https://fizz.ca/en/faq/how-do-i-subscribe-to-fizz-home-internet

This is a good time to join Fizz as they are giving $50 bonus credit to new customers (until January 6 2021).

If you need a referral code, there is a list here:
https://community.fizz.ca/questions/2198337-place-referral-code

You can choose mine or the code of someone who has helped you.
To be transparent, both parties will receive the bonus credit once you have paid your second bill.
Welcome to Fizz!