How to change "." to "," in a temperature item?

Setup, Configuration and Use Scripts & Rules
1

In a rule I use an item which shows the temperature like this for example: 3.5 (type: number, dimension: °C)

So far so good, but when using Alexa it does not say the point “.” at all. I think I need to change the point with a comma here.

Question:
How can this be done?