MICROCELL HAS BEEN DISCONTINUED
As I mentioned back in October, and it bares repeating now, the MicroCell has reached its End Of Life as of Dec. 31st. AT&T has already stopped selling units online and the only place to find a new one from AT&T is at a corporate/retail store as long as inventory lasts. You may be able to find one on eBay but there are caveats to purchasing from there which are covered in my Tech Guide (see link in my sig line). AT&T claims that they will continue support thru a period of time next year but that is probably not true. Support will just try to get you to switch to WiFI-C (WiFi Calling) which does offer better call quality and reliability but you will still need a post paid AT&T cellular account, a phone that is capable of WiFi-C, and a service area that has been provisioned for HD Voice (which most areas should already be).
WiFi-C requires two of the same four ports that the MicroCell requires. Sometime next year AT&T will probably stop supporting/maintaining the two ports that the MicroCell uses and allocate those resources elsewhere, so even if your MicroCell continues to work in 2018, at some point in time it will cease to be able to reach the AT&T Mobility Servers, without notification, and there will be nothing that can be done.
Seriously plan on switching to a phone that is WiFi-C capable, purchase a cellular booster (CelFi or weBoost) or switch to a carrier that offers better coverage in your home.