If you’re using Gmail, you could try the “+” or “.” tricks: https://www.thewindowsclub.com/gmail-address-tricks

EDIT: note that this doesn’t work on all sites, and I have never tried it with Koodo.  I know it used to work with sister brand Public Mobile a number of years ago, so there’s a good chance that one or the other will work.

So, you have a monthly account with 1 number.

And you opened a prepaid account.

Now you want to add a line onto your monthly plan? If so, just log into your account and go to " add a line.

If you want to open up another prepaid account, then you need another email address.

No, our email account is on Hotmail.    “Now you want to add a line onto your monthly plan”  the line I want to add is a prepaid one, so I guess I now need two email accounts? Thanks to both for the replies. 

Actually, the “+” trick works with Hotmail.  (I just tested with both an @hotmail.com and an @outlook.com email address which I have.)

So let’s say your email is somebody@hotmail.com (just for example), you could create another prepaid account as somebody+koodoprepaid2@hotmail.com.  Any emails the system sends to somebody+koodoprepaid2@hotmail.com would end up in your regular somebody@hotmail.com inbox.