I used to do tech support for a cell carrier. We had to be careful about unlock requests because sometimes they were from scammers calling about stolen phones. Only the account owner could request an unlock, and if a phone was flagged as lost or stolen, then we could not unlock it, no matter how much the caller complained. If a caller requested to unlock multiple phones, then that was an immediate red flag. In those cases we were told to try to get the IMEI numbers of the phones (so that we could report them) but not unlock them.
A man called me and asked to check whether some phones were eligible for unlock. Immediately I was suspicious. I asked for the IMEI numbers. He gave me one. I then asked for the others. He insisted on giving me only one at a time and checking one at a time, allegedly so that he did not confuse them.
I do not remember whether the phone was eligible for unlock, but I said I needed the account owner. He said he had bought the phones refurbished from the carrier to use with his business. I again said I needed the account owner. He insisted he did this all the time.
I again insisted that I needed the account owner. He then unloaded a long series of profanities at me and eventually hung up.