Ok, firstly
Secondly, the modem that you have bought from eBay is
technically still the property of Virgin. The person that sold it to you has done so illegaly as they had no right to do so.
Thirdly, you should be aware that only one modem can be in use on one Virgin connection at a time.
Fourth, you should know that only VM approved hardware is allowed to be connected to their service.
Finally, you should know that unless you have a legitimate contract with Virgin to provide a service and are using legitimate Virgin equipment supplied by them (or approved by them for connection to your service) you won't receive any further help here.
Hope that goes some way to answering your questions