STEP 1: Get your ICCID from System, General, About.
STEP 2: Get PhoneItiPad form here for $19.99 and write down your ICCID when requested.
STEP 3: Now on your iPad, open Cydia and add the following repository (app.iphoneislam.com) then search for PhoneItiPad and give it an install.
STEP 4 : Congratulations you now can make Calls and send SMS message, you can check the video made by iPhoneislam below :
You should think twice before giving out your unique ICCID to a third-party, but that seems to be a requirement to be able to make calls on the iPad. If the video above is to be believed, this hack works very effectively and is well worth the $19.99.