upgrade expiration?

Where did you see that? In mine I do not see any date.

I do not see the porblem, you have the 250Mb applied this month and they are valid for 90 days including thus month (data last for 30 days hen rolls over for 60 days), it think that is correct, next month I believe that you will have an other 250

Every upgrade will show an expiry date of 90 days once activated, but don't worry it will be renewed for another 90 days. It will go like this over the 24 month period. Since the upgrade has the longest expiry date, it will be the last one to used. Data with shorter expiry date is used first.