Xfinity mobile

I know that the website said up to $830 for the exchange. But I spoke to customer service and they said that if I finished the portability and trade-in I would get the maximum discount of $830, so I changed my carrier, also because I was unhappy with the service. But now Xfinity only shows the $430 discount, so I complained and they said it would be resolved in 24 hours. I've spoken to several attendants and nothing.