Sadly, not really. The trick is to find that killer plan that you qualify for as a new customer and pounce on it :)

PRE and POST paid are almost operated as separate companies. You do qualify as a new customer.

As many previous posts have advised, use up all your boosters and do the switch at the end of your billing cycle… there are no refunds or credits for unused minutes/data/$.

If you can wait for another billing cycle, there might be some post paid plan deals ( back to school promotions) that you can take advantage of.  Usually start seeing these around mid August.