It depends on what you mean by “calls”. Some Android tablets can make traditional calls, provided they have a SIM-card slot. There are usually various types of tablets with either Wi-Fi only or Wi-Fi and SIM-card slots. A SIM-card slot doesn’t necessarily mean that you can make traditional calls with the tablet, but is often intended to provide internet connection through the mobile network. Talk to your operator and consider if you find this feature important. All tablets can be used for internet communication, as long as they have an internet connection. In other words, calling through services like Skype and Facebook Messenger works just as well from a tablet as from a phone. Tablets from Apple can also run Facetime.