Sister Mobile

This " Sister Mobile" Sprint MVNO I hadn't heard of until today. Looks as if they have some good, cheap phone deals, some of which come with a free month of unlimited talk & text.
Seems as if Tello offerings are better, but I suppose one can get a phone deal at Sistermobile and switch to Tello. $63.20 for an A+ LG X Power along with one month free talk and text isn't bad, but I'm not sure what is meant by, or how long, "this phone will be locked to Sister Mobile Service only".

"This cell phone comes with One month free UnLimited Talk and Text provided by with Sprint coverage.

*WIFI DATA is free and available, Mobile Data sold separately, this service only comes with on Sprint coverage area.
After the month of free service, the plan starts $5 a month. Check details on

High-Capacity Battery: With a 4,100 mAh non-removable battery, the LG X powerâ„¢ phone gives you the power to do more between charges. Quad-Core Processor: In order to give you the speed you need, the X power features a 1.3 GHZ quad-core processor for lightning-fast operations.

This phone will be locked to Sister Mobile Service only"

I imagine the serial number lock is probably FED based, or custom software based. Either way, it'd be a pain if you can't release it. Never heard of this "Sister Mobile" before, but their website does not instill confidence of around-the-clock tech support. To each their own, I guess.