Give it some time. I don't know if there are system design quirks on these refrigerators that may cause them to operate differently from other makes. For sure if yours is working at bringing the cabinet temperature down to the 37-40 range, it could run for a while.
Do you have the cold control on the warmest setting? That would be a good way to determine whether there's another problem, although I can't imagine what else would cause the compressor to keep running if both the thermostat and relay have been replaced. Do you hear a click when you adjust the cold control lower or higher? That would indicate that the contacts are opening and closing properly.
Perhaps it's a wiring issue. Do you know whether anyone has messed with the relay or thermostat before?
Do you have the cold control on the warmest setting? That would be a good way to determine whether there's another problem, although I can't imagine what else would cause the compressor to keep running if both the thermostat and relay have been replaced. Do you hear a click when you adjust the cold control lower or higher? That would indicate that the contacts are opening and closing properly.
Perhaps it's a wiring issue. Do you know whether anyone has messed with the relay or thermostat before?