Just get it done at a apple store as I did today. It’s £25 with a 90 day warranty and your phone is still waterproof, and it’s a genuine battery. I have had so much trouble with “genuine” and oem quality apple batteries in the past. Not worth wasting the money
my iphone 7 which is on 11.4.1 has the greyed out speaker. It has 71 days left on the warranty, and i have an appointment with a certified apple repairer. I am going to try and get repair or replacement
You say, they refuse to repair a phone, they broke themselves. Was it a Samsung authorized shop, or Samsung themselves? If it was the latter, then they are responsible for it. In the uk I would contact trading standards and see what they say, but i am not sure what country you are in.