The only setting I would think of would be the regional setting. That is accessed via Settings>General>Language & Region. However, what troubleshooting have you tried? If the device is unlocked and you are receiving service and able to make phone calls, then the SIM should be recognized. I would try a reset of network settings just to be sure. Go to Settings>General>Reset>Reset Network Settings. After the phone restarts, see if you are able to receive the calls. Otherwise, your carrier would need to troubleshoot that, since the iPhone does not really have any setting that prevents particular calls from being received except Blocking, but that would not block all landline calls. The carrier should be able to see if the calls are getting into the system.