Need Sim Card for iPad At&t 4
Can I purchase a Sim Card? I purchased a used iPad 4. Would like to add air time & be able to tether to laptop or another iPad. On my old iPad 1 3G At&t I have been purchasing a ! gig for $25 airtime that lasts up to 3 months if not used up before then. I want to do the same with my new iPad 4 & be able to tether to my laptop or other iPad. Is it as simple as purchasing a sim card. Then refilling as needed. Is there separate tethering charges?