Which ISP are you with Sacchi1412? If onvol, go to www.onvol.net and cllick on 'sign-in to self-care centre'. You will have to enter the account number and pin number which are shown in a box at the bottom side of your bill.
If you're with GO, go to www.go.com.mt , click Surf, and somewhere along the side of the next page you should see an Internet Management link. All you have to do there is enter your username and password.