If you are divested and roaming on Verizon *228 does not work. You have to edit the settings to force the phone to Sprint to update the prl. Forcing the phone to Sprint by using *228xx wont work.
If you are retained (getting a Verizon bill now) and have an old prl thats got you roaming on Sprint, you can use *22800, *22801 to for the phone to Verizon and update the prl.