Is it firmware or the actual screen thats the issue (Desperate help)

So, I have a iphone 6 twas working super fine for about a year and 6 months. All of a sudden a few updates happened and things got worse.

1* . The iphone would be super untouch responsive (when I locked screen and unloked I could use the screen for around a few minutes then it would go back to being unresponvie and so fourth).

• 2. I removed the case from the phone and the screen protector, wiped data and restored backup. (worked for a while like 2-3 days and went back to normal) THE only apps I was using is whatsapp and spotify
• 3. Fully wiped the phone started using it as new, the phone worked for a week had the minor issue again
• 4. over time it has gotten worse and now the screen does what it wants with out even touching it. The unresponsive touch does not work ect,

Not sure what the problem is, a guy told me a wire may be corroded but thats strange. As a last resort I might change the screen and see if that works.

notes: No water damage, no damage to the phone (has not been dropped) phones in grade A* condition.