Hello @DeniseD25568 ,
Without getting into too many account specifics for security, I can say that it looks like your billing tier increased because of a sizable increase in your contact numbers this past month. Since you passed the threshold for the previous tier, your pricing adjusted for this billing cycle accordingly.
I did notice in the last email you sent out, that you have a large number of bounces. It may be worth deleting / unsubbing these bounces so your tier can reduced to its original level. Once you do that, reach out to our Billing team for an adjustment, and point out that you haven't sent to the number of people that put you over the threshold so they can make sure you're compensated for the difference. If you choose to send out to all of your contacts before deleting the duds, then your pricing will remain the same and our Billing team won't be able to do anything.