Why my Iphone6 still home screen Freeze after following all advice from Apple website?

So for the past 2 weeks plus my Iphone6 started to Freeze after both IOS update. I have contacted the online Apple support and even Live chat to follow their advice/instructions. From Shutting off the phone, to re-setting and to even Factory reset. The problem still persist with now even more worst than what it was. Now in order for me to even open an application (message), I have to complete shut off the phone (Apple Logo) and restart it, just for it to function for few minute and it goes back to a "Freezing/non-responsive" phone.

So I decided to visit the Apple store and first and most the individual who greeted me was kind of rude. Secondly that same individual was my support tech adviser.

To my surprise first the Tech stated the Phone looks remarkably great and well maintained, and as I explained that I have always maintained the phone in a protect case and very well care for. As she proceeded to do an diagnostic test, the phone pass with no problem. Now the visual test according to her exam "the phone has a slight bend by the volume button" she proceeded to show me in which I didn't notice no such.

She continues to show me and made the statement as the reason "screen freeze, is because the phone is slightly bend" I told her that's impossible as the phone has been function very well until the last IOS upgrade, in which it was the first upgrade since having the phone for 2 years. Well to her surprise and mines now the issue is due to "old phone" and after two years, its like a car when "warranty runs out" ok some one please explain this to me...

To summed things up, I was offered a replacement for the charge of $129.00 plus tax and 90 days warranty and that this is a one time offer... I left the Apple store disappointing with no phone and now after so many years deciding not to support Apple.

Sorry for my long post and rant, but I would like my phone back to it function before the update IOS. Please someone advice or give a better advice to atleast be able to answer calls as it wont allow me to do so, or it decided to open application on its own.