Am I obliged to buy a new SIM from Fizz or could I simply use my old SIM? I have to buy a new SIM from Fizz, will I be able to keep my old phone number?
Yes you need to buy a SIM from Fizz if you want to transfer your number when you activate a plan.
This is the guide https://fizz.ca/en/faq/activation-how-do-i-transfer-my-current-phone-number-to-fizz
You can buy a SIM at the UQAM's coop or couche tard https://fizz.ca/en/couche-tard-sim
Please remember to use a referral code when you activate your plan, this is the guide https://fizz.ca/en/faq/how-do-i-invite-friends-to-join-fizz, you can only insert when you activate the plan, when the order summary is shown before the taxes, click on the green button to confirm. You can pick one referal here https://forum.fizz.ca/en/discussion/2198337/this-is-the-place-for-your-referral-codes-here-and-only-here or you can take mine, I am almost three years with Fizz.
If you activate today or tomorrow using a referral code, you and the other person (the owner of the code) will get 75$ each.
You can use your old phone number. Just do transfer your number option when you place your order. Use my referral code if you'd like and we both will get 75$
When you transfer your current phone number to Fizz, your line must still be active with your current/previous provider. We will disconnect your old provider during the activation process.
To keep your number and transfer it to Fizz, you will need the account number for your current/previous mobile provider (you can find it on your bill).
During the activation process, here’s how to keep your current phone number:
Am I obliged to buy a new SIM from Fizz
Yes you absolutely need to use Fizz's SIM card. It acts as a network identifier for them.
or could I simply use my old SIM?
Keep your old SIM in case you are not satisfied with Fizz' network. Same goes with Fizz's card: if you ever decide to leave Fizz, it can be reused by a new customer (resold, given, kept for yourself,...).
I have to buy a new SIM from Fizz, will I be able to keep my old phone number?
Yes. The exceptions are for landline or VoIP numbers which are not your case.
But keep in mind that your account holding your phone number must remain active at your previous service provider while Fizz handles the transfer.