Indeed, @JonathanEllis , changing one's number is easy.
However not to any number. It has to be within the 'family' of numbers TELUS uses and not a currently used number assigned to another customer.
So getting a specific number is practically impossible, unless it's a number one already has registered with an active service with another provider which can be ported over here to Public Mobile.
You login on your desktop browser or put your phone browser mode click on your profile then the pencil icon you should be able to change your number and within 30 days after activation four times that’s what it says for me , respond if you need more assistance
@Kimmis the number you "used before" , what you meant by that?
If it is an active number with another provider, you can request porting the number into PM. Just go to My Account's Profile page, click Transfer number
But if it was just a number you used before and you cancelled that account, then it depends
If the number you want to get back was originally from another provider and you just ported into PM, then PM support would not be able to assign you back the number. The number would have been back to the original provider where you got it from in the beginning.
However, if the number you want back was from PM/Koodo/Telus originally, then there is a slight chance you can get it back, given that no one has taken it yet. You can message support and ask