I highly doubt that there is a way for public mobile to associate your account with a device that does not contain a SIM card slot.
If it was a question you need a definitive answer to, you could ask the public mobile moderators for an official reply.
To contact a moderator, there are 2 methods:
Watch for their response in your Community private mailbox which will be indicated by a number on the small envelope icon to the left of your Community avatar.
Here's an article from TELUS regarding the shutdown up to CDMA a few years back. Indeed, the CDMA device I had was the most reliable phone I've ever used, structurally, battery-wise, and with respect to voice quality.
But as the saying goes, all good things must come to an end.
It looks like you will need a new phone. You can get the new flip phone or a new smart phone with a SIM tray from London Drugs, Walmart or Mobile Shop (Loblaws) and they can activate the PM SIM for you.
Is it possible to use public mobile on an old flip phone from Telus that doesn't take a sim card?
Sorry, but you won't be able to use this phone anywhere in Canada.