It sounds like the Apple Repair Centers. I was going to hand my iPhone X down to my daughter, but it needed a battery, according to the battery health analyzer in Settings. The thing worked fine (except that it said I should replace the battery) and had always been in an Otterbox Defender case. So, I opened a support case, paid $69 plus tax and shipping, and had a box sent to me. I sent the phone in to the repair center, then the next day I'm notified the repair is on hold.
They tell me that after disassembly, there's a problem with the connection to Wi-Fi, and now it'll be $549 to repair, or, they can send back my now-worthless phone, unrepaired, or recycle it. I had them call me, then then spent 45 minutes on the phone with an agent, then their supervisor, asking asking how my phone that had worked great for three years was mysteriously broken after they took it apart. Finally, they granted a one-time exception to repair the phone, and only charge for the new battery (I wonder how often they have to do that?).
A couple days later, a box shows up from Pennsylvania (I sent the phone to Fort Worth), with what I assume was a refurbished phone in it (a different serial number from the one I sent them).