Non-removable batteries are meant to stay in the device, but since people still want to try and remove it T-Mobile has deciced to stop selling the ZTE Zmax.

ZTE Zmax sales halted at T-Mobile

People love being able to remove batteries from their phones, and some will even do it when the battery is not meant to be removed. T-Mobile has put a stop to selling the ZTE Zmax for now because people are attempting to remove the battery that is meant to stay in the device. The back of this device is not even meant to be removed, but since it is only clipped, people are using brute force to get it off. At this point it is unknown whether the devices were locked up, users wanted to reset the device, or exactly what was going on that made people want to get to the battery. Some people even went as far as using knives and screwdrivers to gain access.

T-Mobile has pulled the device from its line-up after having it around for only seven months. We are unsure of how many people have tried to remove the battery, but we would imagine it was more than just one or two people who caused T-Mobile to pull the device. It is unclear at this time whether or not it will make another appearance, but T-Mobile has apparently voiced their complaints to ZTE. At this time ZTE urges that users experiencing issues with the device take it back to T-Mobile instead of attempting a repair of their own.

Source: PCMag