Hello
If you are using a personal Microsoft account, you will not see the Call option.
This call option is for those on business license AND have the phone/calling plan add on licenses.
If the reason you asked about this is because you want to use any remaining Skype credits, use the Skype Web Portal: https://calling.web.skype.com
If you need to reactivate your credits, sign into here: https://secure.skype.com/portal/settings/credit/reactivate