The rep at a Telus store was probably only having access to Koodo and Telus plan. They did not have information on public mobile. Public mobile is a self-serve brand, their information was online and customer has to check themselves. It cut cost by doing that. Anyway, those plans on public mobile/Koodo are divided into 3G and 4G "speed", i.e. they are on the same network but data speed was throttled to certain speed limit. 

To revert back to your public mobile service, you would have to contact public mobile customer service first, tell them about the situation and see what they can do. I don't think Koodo customer service can put you back into a public mobile plan as they don't have access to public mobile system. However,you can contact them to ask them to make sure you didn't had any additional cost besides service of few days with Koodo. To contact Koodo, go here www.koodo.com/chat and type "I would like to cancel".

You should be able to go back to Public Mobile, as long as it is within 90 days of non-payment. Do you still have access to your account?

Once that is done, you can initiate the porting process and your Koodo account would be automatically cancelled. https://publicmobile.ca/en/on/get-help/articles/reactivate-a-suspended-plan