Apps for travel

[Wrthomas69]

I currently own a galaxy S4 from AT&T. I will be traveling to Cancun Mexico and I am looking for apps that I can text with and make phone calls from Wi-Fi only the hotel where I am staying has free Wi-Fi and I am trying to not have a $500 phone bill. I need both a texting app and a calling app that uses Wi-Fi rather than the cell network also if there is one that does not require the person that I am texting or calling to have the same app can I call or text someone simply using their phone number. A TNT simply charges too much money to use their network in Mexico $30 for 200 texts and $30 for 60 minutes of phone calls I would like to install these apps on all of our families S4's we currently have four identical Samsung galaxy S4's. Thanks in advance for any help that anyone can give.