unlocked nokia 640 lte wont work with net10 sim

[suny32]

hi, i purchased a nokia lumia 640 lte a few weeks ago. i paid a service for an unlocking fee for the phone and then i purshased a net10 50$ unlimited / monthly service sim for it. the phone seemed to work fine for a couple of days then... nothing. only an ATT operator every time i try to dial out. i still received 4G LTE service for a few more days, now i just dont know . my month is about to be up and i have not used but a few of the service days that i purchased. is there something wrong with my phone??.....blacklisted? why am i having so much trouble with this windows 8.1 phone??? how do i find out what is wrong?

[NET10 - Jhonally]

Hi suny32. My name is NET10 Jhonally. Sorry that you’re having a problem. I will contact you directly with a private message. Thanks.