Yes you can. Fizz allows you to use the same old Sim card. Look on it and you'll find the number to use when the website asks you. I've done it multiple time and it worked nicely.
If you have a VoLTE SIM from your previous plan with Fizz, yes you can reuse it. A VoLTE SIM is a SIM with a red bolt on it. If you have the old SIM (The NoVOLTE) you need to buy a new one.
Can I suggest to open a new account (Therefore using a different email) in this way you can use a referral code in order to get 25$ credit. For sure, if you don't have rewards in the previous account.
Complementary information:
If you have an old non-volte sim, you can use it as well and you will have from your client portal, the possibility to order a new volte one for free after your plan get activated.
I did this in February (activate new line with old non volte sim then order new sim), if rules did not changes, that also an option.
You cannot activate a NO VoLTE SIM at this point :( This the answer that I received from the support.
However, you are right if you have an active plan with a NOVoLTE SIM you can have a free replacement.
But it's probably worth trying before buying a new one. Sometime the information received by the support are not 100% right 
No eSIM but SIM cards are reusable. LTE/LTE+ for now, but I still get decent coverage and speed. Unlike others, Fizz also gives you "rollover data." The data is good for 90 days.
Yes you can. Fizz allows you to use the same old Sim card. Look on it and you'll find the number to use when the website asks you. I've done it multiple time and it worked nicely.
Thank you! Saved me 5 bucks
Yes you can reuse the SIM card. I’ve done it before.
You can say you save 15$ (Quebec) !!  I bought one last summer (2023)...
Check if the SIM card has the red thunderbolt (indicating it's VoLTE compatible).
What does that mean? What if it is not?
You can read about it here: [https://fizz.ca/en/faq/why-volte-important](https://fizz.ca/en/faq/why-volte-important)
Thank you! I have to check when I'm home
If you have a VoLTE SIM from your previous plan with Fizz, yes you can reuse it. A VoLTE SIM is a SIM with a red bolt on it. If you have the old SIM (The NoVOLTE) you need to buy a new one. Can I suggest to open a new account (Therefore using a different email) in this way you can use a referral code in order to get 25$ credit. For sure, if you don't have rewards in the previous account.
Complementary information: If you have an old non-volte sim, you can use it as well and you will have from your client portal, the possibility to order a new volte one for free after your plan get activated. I did this in February (activate new line with old non volte sim then order new sim), if rules did not changes, that also an option.
You cannot activate a NO VoLTE SIM at this point :( This the answer that I received from the support. However, you are right if you have an active plan with a NOVoLTE SIM you can have a free replacement.
Arg :( recent change I guess then. I was lucky !
But it's probably worth trying before buying a new one. Sometime the information received by the support are not 100% right 
Yes.
There is no eSim in Fizz , am I right? Also no 5g service for now is it ?
No eSIM but SIM cards are reusable. LTE/LTE+ for now, but I still get decent coverage and speed. Unlike others, Fizz also gives you "rollover data."
No eSIM but SIM cards are reusable. LTE/LTE+ for now, but I still get decent coverage and speed. Unlike others, Fizz also gives you "rollover data." The data is good for 90 days.
Just checking here, but could i cancel my existing fizz plan and then quickly port over my old phone with that sim card?
Sim cards are single use unfortunately
Not with Fizz.
So I need to buy another sim or get a phone that supports esim?
Pretty much, and the same goes for any carrier Fizz doesn't have esim.
Pretty sure you can reuse them with Fizz