There's a few situations where this might happen.
1) Are you on a metered traffic product? Such as data storage, media Content Distribution, or have metered bandwidth?
If so, you may have had more traffic to your site than usual last month. We can gladly provide a complete breakdown of traffic, origin of the traffic, and how much bandwidth was used according to our hosting provider.
2) Is this a new line item completely appearing on the bill?
If there's a line item you don't recognize on the bill, send a ticket, and we'll be glad to discuss the bill in detail
3) Is something on the bill higher than usual?
If something on the bill seems higher than usual, give us a call, and we'll explain your bill.
When opening a ticket, please include the number on the invoice, as well as any charges that may have already applied to your credit card so we can sort everything out for you. Overcharges can be refunded, or used as a credit towards a future bill.