What exactly do you see?
Blacklisting means something very specific. It is possible for a carrier to blacklist a stolen device, and I believe they can do that at the behest of your insurance company. If you truly mean "blacklisted" you would have to contact your insurance company (and possibly reimburse them) and/or your carrier.
If you mean Activation Lock, read: How to remove Activation Lock - Apple Support There are only two ways to remove an activation lock:
#1 If you have the necessary information, you or the signed in owner can do this yourself by simply signing in with the owner account and password information and doing as instructed in the above article. If you use this method and this is a new device to you, follow unlocking by doing as outlined in What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support or What to do before you sell, give away, trade in, or recycle your Mac - Apple Support . If you do not have the required information then you can try method 2 —>
#2 Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Read the requirements and steps for an Activation Lock support request at: https://al-support.apple.com/#/additional-support and links at the bottom right for the type of service requested. Apple says they “may” require "proof of purchase documentation” and that you need “proof of ownership documentation”, but does not detail what currently constitutes proof other than it “must include the product serial number, IMEI or MEID.” User reports on this community indicate that typically Apple will absolutely require, and ONLY accept, an original receipt issued by Apple or an Apple Authorized Reseller. Presumably this is the only kind Apple can authenticate against fraud since Apple is not involved in third party sales. Apple recommends that you "Keep your receipt after you buy an Apple device" --> Keep your receipt after you buy an Apple device - Apple Support
If Apple resets the device this will give you access to the device but won't restore access to the account used to lock it. There is nothing that can be done to expedite an Activation Lock request.
If you cannot get the device unlocked then read this section from the very bottom of Apple Trade In - Apple :
"Does Apple offer recycling?
Yes. Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on Apple for free. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way."
