I called up t-mobile cause I was having low to no signal in my house and they asked me if I had Wifi and I said yes. So the guy told me that Wifi calling not only allows me to text over Wifi but also send and receive sms/mms messages. So far the SMS messages is true but the mms messages will not download over Wifi, he did tell me that the phone has to be connected with the Wifi calling and I am but it still won't work and it's really getting me mad that it won't work right. Even if you go to the setting and look at the info that they give you about Wifi calling it says send and receive SMS and multimedia over Wifi.