Texting is a telephone function. The pad is wifi only, so no telephone network access. There are paid services that translate short emails into texts, or you can use apps like Hangouts.
If you have internet through WiFi, you can send an Email to a cellphone number but you need to know what network they are on.
For instance: 1-222-333-4444@txt,att.net
Altel @sms.alltelwireless.com @mms.alltelwireless.com
AT&T @txt.att.net @mms.att.net
Boost Mobile @sms.myboostmobile.com @myboostmobile.com
Sprint @messaging.sprintpcs.com @pm.sprint.com
T-Mobile @tmomail.net @tmomail.net
U.S. Cellular @email.uscc.net @mms.uscc.net
Verizon @vtext.com @vzwpix.com
Virgin Mobile @vmobl.com @vmpix.com