Usage Meter issues can occur, but are rare. As will always be the case otherwise, the usage has in fact been used.

It should not be refered to as a problem that needs to be fixed, or that requires a change of provider, this implies it is an ISP issue, whereas it is a matter that the users PC, PC's, etc have used the data.

Disconnect power from the modem overnight, then ask your ISP for an hourly report from a few days ago till now, you will see the usage is zero for that downtime.