The temprature is over the start sign although the engine is cold :Aveo 2007 korean made

I have only problem in the engine temprature sign only in the start of the engine on the morning "cold engine" the sign is above the start point not below the sign although the enigne is just started on the morning and every thing is fine after the engine get warm, the sign of temperature not exceeding the middle, and the engine in normal voice with not high RPM, I went to service to fix the problem but they told me nothing in my car? And they checked the engine when it warm only, what can I do?