If you want one for free, try calling 611, probably will need a supervisor or go to a store that is a corporate store. If you aren't aware, some previous AT&T stores are actually like 3rd party retail stores now and will even charge you for a SIM card.
Get the manager in the store. Tell them your phone is draining at home with the bad signal. They may just offer you a microcell for free.. Depends on the manager. If they want you to buy it, tell them you understand that TMO has LTE boosters for free, will pay up to $650 per line to switch and give you 10 gb a month pet line, of data (all true BTW).
You can use the above with 611 or the store, if you try one and they say no, move to the other one and try. You can also ask for the retention dept at AT&T and can tell them if they don't give you one, you will be forced to check out TMO.
If you just want to ask and they say no and you don't want to push, then you can buy one in the store. Have them set it up online there, they can put in the AT&T numbers that will use it.
Now again, that is only for 3G talk signal, but it will stop the drain from a bad signal and stopped missed calls. I just think it should be free to customers that need it. You will have to hook it up to your modem or router, so you need a free port for it.
The drain is some app, but not sure yet what is causing that.