Anyone had issues with glitchy buggy iPhone 6?

I am on my second iPhone 6. My first one was constantly glitchy and iMessage was acting really strange. I would send someone a message, which it would send, but a few seconds to several minutes later, my phone would go off as if I had a new text. I would look and my text I had sent someone else, was also sent to me with the blue dot next to it (it didn’t do it with all texts). Too, people I had sent a link or pic of something to, said that they got it, but when looking later, it disappeared even though they didn’t delete it. Sometimes when trying to txt a short video I took, it wouldn’t send it saying that it was corrupt. My phone would also freeze at times, where when I’d swipe to open, it wouldn’t open (it acted as if it had been exposed to cold where nothing works). I must’ve did a hard reset about 11 times over the course of 2 yrs. Whenever I updated it, it would help for a bit, but then full on symptoms soon appeared. I don’t use any apps other than what comes with my phone and I never click on a link that is sent from someone I don’t know. The last thing that happened, is when someone called, I could hear them, but they couldn’t hear me. The last time attempting to hard reset, it wouldn’t let me and kept asking for my passcode and upon entering it, it wouldn’t work and trying to reset that was a nightmare, so I gave up. So, with all that said, my sister gave me her extra brand new iPhone 6 (she got it bogo) and it was so refreshing to have a phone that works wonderfully, for such a short time, but guess what? The message thing is happening again!!! Any help/opinions are very appreciated!