Could Not Activate Cellular Data Network
Your carrier is passing the buck. Apple has nothing to do with cellular activation unless you buy the phone directly from Apple. The carrier should know that and treat you to correct explanations.

Try reviewing the swappa article on IMEI / MEID / ESN


https://swappa.com/faq/answer/share_esn_numbers


You are likely buying blocked devices and should contact the seller if possible to arrange return and refund unless the listing says clearly these are for parts and not operational. Ebay might be of help if you can’t get the seller to assist or explain the device isn’t blocked if your research shows the issue is a blocked device.