Not all smartwatches have functions for making phone calls. For those that have this function, you should consider one aspect: If the Smartwatch does not have a SIM card slot in which you have inserted a SIM card, the phone call only works if your smartphone is also nearby. Then it transfers the call to your watch. If, on the other hand, you have a Smartwatch with a SIM card, it connects directly to the mobile network and lets you use the Internet everywhere - even if you don't have your smartphone with you.