apple service center declining repair request.(under warranty and apple care plus is purchased too)

When they say beyond economical repair that usually means the damage is excessive, missing parts, or appears to have been intentionally done. Basically it’s using the terms for AppleCare+ https://www.apple.com/legal/sales-support/applecare/applecareplus/2209/220907_applecareplus_us.pdf

Apple will not provide Hardware Services or ADH Services in the following circumstances:

(a) To protect against normal wear and tear, or to repair cosmetic damage not affecting the functionality of the Covered Equipment;

(b) To conduct preventative maintenance;

(c) To replace Covered Equipment that is lost or stolen;

(d) To repair damage caused by reckless, abusive, willful or intentional conduct, or any use of the Covered Equipment in a manner not normal or intended by Apple;

(e) To install, remove or dispose of the Covered Equipment or the equipment provided to you while the Covered Equipment is being serviced;

(f) To repair damage caused by a product that is not Covered Equipment;

(g) To repair any damage to Covered Equipment (regardless of the cause) if the Covered Equipment has been opened, serviced, modified, or altered by anyone other than Apple or an authorized representative of Apple;

(h) To repair pre-existing conditions of the Covered Equipment if you purchased the Plan after you purchased the Covered Equipment;

(i) To repair any damage to Covered Equipment with a serial number that has been altered, defaced or removed;

(j) To repair damages caused by fire, earthquake or other external causes;

(k) The loss of, loss of use of, damage to, corruption of, inability to access, or inability to manipulate any electronic hardware or software, or components thereof, that are used to store, process, access, transmit, or receive information within Covered Equipment as a result of any cause or loss other than covered losses specifically stated in this

Plan, including any unauthorized access or unauthorized use of such system, a denial of service attack, or receipt or transmission of malicious code; or

(l) The loss of, loss of use of, damage to, corruption of, inability to access, or inability to manipulate any electronic data stored within Covered Equipment, including any such loss caused by unauthorized access or unauthorized use of such data, a denial of service attack, or receipt or transmission of malicious code.

If at all possible, go in person to the Apple Store. Those guys are always helpful and will give you the guidance you need. I know it is a pain to go there but it is worth it. If you'd prefer, call them as sometimes simply filling out the documents online don't quite capture the nuances of what you're trying to express.

What country are you in? What country was the device purchased in?

The warranty and AppleCare+ are ONLY valid in the country where the device was originally sold.