Upgrading Phone.

I am looking to get rid of the LG X Charge I got when I signed in to XM a couple of years ago.  Looking to cash in on the iPhone sale going on currently. 

Question:  If I go to the store and buy the iPhone cash no finance will Xfinity still do a credit check on me.  Reason I ask is twofold.  First, I have heard the horror stories of folks, even with great credit, being denied for seemingly no rhyme or reason.  This makes zero sense to me and cannot fathom why any company that wants to make money would do this.  Secondly, I have all my credit reports frozen and have little desire to unfreeze them for a sale that should not require a hard credit check in the first place. I mean seriously Comcast, I an not buying a new car here.  May just be easier to just buy a XM iPhone on Swappa and swap SIMS.  Yes, it works.  I have friends who have done this. 

Any input here from the Comcast Reps would be appreciated.  To be honest, I am just plain too old to deal with any grief and aggravation I have read about here for just a cell phone.  Thanx. 

BTW, please do not ask me to PM because I cannot do that and no one over the years has bothered to find out why.  I click on the name and the PM button that is supposed to be on the right of the screen is not there and never has been.  Thanx again.