Hello and welcome to just answer
It sounds very much like you have either a flap control motor fault or a temp sensor fault. You will need to have the fault memory checked of the air con system to sww which one is playing up. If there are no fault codes stored you will need to have the measuring blocks checked to see which sensor is reading the wrong temperature.
I hope this helps and if I can help further please feel free to ask.
where should i take the car for diagnostic check, is it audi only? thanks