The incredibly clever modders over at XDA developers have managed to find out a way to enable phone calls on the Samsung Galaxy Tab.
It started with a forum member, Jyveafk, rooting his Galaxy Tab and trying to install the phone.apk module on it. After failing quite a few times, and some trial and error, Jyveafk finally managed to flash his Galaxy Tab to enable phone calls on it.
The method is a bit complex and is recommended only for experienced flashers. You will need the Odin3 Flasher to carry out the mod. For more details, check out this detailed tutorial – US T-Mobile Galaxy Tab flashed to make phone calls – Tutorial. The method works only on EDGE for now.