There are also apps such as Talkatone that allows you to make calls from the iPad. Obviously, they won't be the same as using a cell phone, but you can use them to call regular landlines or cell phones.
With Talkatone, you set it up and use a Google voice phone number (you have to have a Google account). It's a paid app that allows you to use the Google Voice service for free (you can pay amonthly fee if you want fancier services)
I've used Talkatone. Not the greatest, but it'll do in a pinch. It got my brother-in-law to my location where he was able to help me with my car troubles - back before I had a cell phone. So, there's that.
Marilyn