AT&T Next

I bought a Galaxy S6 edge from best buy online back in April or so. I haven't really been paying attention to my bills until recently and realized they never started charging me for the phone. I checked online and it says my phone is pending an AT&T next plan. Has anyone experienced this and what did you do about it? I don't really want to go to AT&T and complain that I'm not getting charged for it but I also don't want to be stuck with the phone if I go to buy a new one after my phone is supposed to be paid off. Thanks for your feedback and opinions!