Well it is also possible to have one user account (yours) and only allow skype to skype calls (free) - this is easy to do, if you don't buy any credit, paid for calls can't be made anyway. If you really want a facility that allows people to phone 'real' numbers it isn't going to be easy as Steve says on your account. You can't charge by the minute as some destinations are 20x dearer than others per minute.