Hi Minseo
If you already activated your SIM card, you cannot enter the code anymore, your friend was suppose to give your the right information too :(
The referral code must be entered in the field provided at the bottom of the order summary.
If a person forgets to enter the referral code when subscribing, they’re unfortunately out of luck. We cannot retroactively apply a referral code.
Source: https://fizz.ca/en/faq/how-do-i-invite-friends-to-join-fizz
You should close the plan, get refunded, open a new account (new email) and start it with the activation process.
However, if you care about the phone number, you should transfer your account to some other provider
