you can reset PIN here, but you still need to login My Account
https://myaccount.publicmobile.ca/en/account/reset/pin
if you can login My Account, would be easier to to buy the addon from My Account directly
But buying data addon is $$ and it has 30 days expiry.
You said you have a $40 plan for many years? How much data you have now? The current $40 plan probably get you more data, or you might even be able to get more data and pay less every month.
Check your Change Subscription page on My Account to see what better choice you have. You can then use Change Now to make an immediate plan change to get the data right a way
