New or "like new" replacement units

I’ve been having issues with randomly losing connection to the internet over my T-mobile home internet router, even though the connection says it’s up and no errors are on the device.  

After about five calls into customer service, I finally asked for a replacement - during the disclosure process they state they will send you a "new or like new device."  Well, I got my replacement yesterday, and there is what looks to be a water stain on the top, and no power cord provided - if this is "like new" then I am using a different definition.  To say I am furious is an understatement - I run a home office off this unit (remote location, it's the only option I really have), and when I called customer service they kept repeating their disclosure of "new or like new."  What really frustrates me is that they'll charge me the cost of A NEW UNIT if I don't return the existing router and replace it with this.  Nothing I can do - so beware, everyone, if you get a replacement, it may just be something someone else returned.  There's no indication this unit has been tested at all, just thrown in a box and sent to me.  After the multitude of issues I would think a new unit would be called for - when it works it works well, but when it goes down in the middle of important business, I see why people want to get lawyers involved, they are costing *me* my time and money with this.

I will be moving to fiber when it's installed here (it's in the works, but no definite date), that's for sure.  Just wanted to vent since I keep getting the same script from customer service - I have no choice but to replace a unit that I know how to fix when it goes down with some unknown potential.  

Oh, and there's no instructions sent with this.  I got so angry with customer service I just hung up - they called me back and said "don't forget to transfer the SIM from your old router to your new one!" There isn't any way to remove the SIM cover off this model!  This whole process is 110% ridiculous.