Melting point = Freezing Point
Consider a system that contains only a single substance. At the temperature where the solid and liquid phase of the substance are in thermodynamic equilibrium you cannot tell if the system initially consisted only of solid or only of liquid or of a mixture of both.
Thermodynamic equilibrium means that the substance has the same temperature all over the system.
If a small amount of heat is added to the system, some of the substance melts. So the temperature is the melting point of the substance.
If a small amount of heat is removed from the system, some of the substance freezes. So the temperature is the freezing point of the substance.
This shows that melting point and freezing point are the same.