iPhone 8 - My WORST phone EVER!

I'm a "converted" Apple user but the iPhone 8 is fast changing me - This is the WORSE phone I have ever owned. Problems with iPhone 8 since I received it in August 2018. The first unit was sent away numerous times (I had to pay the courier fees) and no fault was found. Yet, same fault existed as no repairs were done. I was asked to change the Sim card... twice (at my cost) with no improvement. There is a problem with the Microphone. I sound ****led and my voice at times does not reach the person at the other end. iStore changed the unit and I thought my problems was over, Not in your life, Same problem. Now iStore want to iStore want to send it away again? What for? Did not work the previous few times, why would it suddenly be fixed now? Everytime the phone gets "wiped" and I need to reset it when I get it back. A real pain in the neck. Is this the phone that is going to cause a "Cheers Apple"? I may soon have a iPhone 8, iPhone 7, iPad (three) for sale.