16200 is from ZTE and 18000 one is from some other company. I got a call from my OSS today to come and exchange my device for the 18000 one because they're apparently getting complaints from users about it losing its LTE coverage (similar problems that I faced before).other than the difference in free airtime of 3 and 4 months, are their any differences between devices in the 13k and 15k packages.