Hello Christinasu520,
Welcome to the community!
Firstly, if you wished to transfer your services from pre-paid to post-paid, you would need to contact customer service to migrate your services from the one type to the other. Yes, Fido previously held promotions for pre-paid customers to migrate their services to post-paid whereby unused balances would also transfer. Unfortunately, however, I don't believe there are currently any such promotions available (see here). As suggested in that post, you might consider trying to use the remaining balance on your pre-paid account before migrating services.
That said, you should note these forums are community-driven and not intended as a venue for customer services. We may not have the most up-to-date information regarding possible promotions. If you would like verify the information, you would need to contact customer service. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above.
Hope this helps 😀
Cheers
