If theonly constant in the world past present and future is change then explain the notion of changing change?

There would be no change if time stands still. Change is therefore defined by the progression of time and the constancy of change means that with every progression of time, there is some change or the other in the space and its contents even though the rate of change may not be linear or universal except perhaps at the gross level of totality. That then takes us into the discussion of uncertainty.