Paid user paying $3/mth for 5Gb. How do I upgrade to new deal of $2.50/mth for 10Gb?

Paid user paying $3/mth for 5Gb. How do I upgrade to new deal of $2.50/mth for 10Gb?

I can't believe I even have to ask this question.
You have repeatedly blocked my mail account because I have slipped over the 5Gb storage limit, and now when I'm just clicking around I see that new users not only pay less but get more storage than your established customers.
So to confirm, you have blocked my account even though I am paying more than a brand new customer who is using more storage space than me?
Is this really the case?