i need to remove the antenna from nighthawk x4s- ac3200 version c7800

I bought this from Amazon (refurbished, stupid move) anyway. I'm returning it for the same issue someone else apparently returned it for. It will not communicate and hook up with the web. So I am returning it to Amazon with not problem. However I can not get the antenna back off. I know they are removable because I put them on and I know I screwed them in  but they do not simply unscrew. Any suggestions? Thanks Todays date is 09/16/2019 If no response for today then don't bother, I'm taking it to them with the antenna's attached if I have too. I've spent nearly two weeks and several hours on the phone with my cable company for it it be this machine. Good lord..what a waste of time.