Just switched from H2O pay-go to their $30/mo unlimited plan.... found that my pay-go balance evaporated. Maybe everyone knew this, but I didn't... particularly also being a PagePlus customer, but that's apparently what H2O does.

Luckily I didn't have too much of a PayGo balance -- I'd be pissed if i lost my PagePlus balance that way, but thankfully PagePlus keeps your balance even as a monthly plan customer.