I was referring to the name of the device, not of the sensor. Lets say, rename LGT-62 to Frezzer Room 503.
Have you tried sending SMS?
Yes, if I name a new device Freezer XXX the SMS will be “ Channel 7 has reached the temperature of 12. This is related to Freezer XXX. So I know, which freezer sent me the SMS via Cayenne. At the beginning I used the device name given by Cayenne and so this name is sent. Therefor I am asking if I can change the device name.
to change the device name, click on the clog wheel (Setting) on the top right of the dashboard.
Short info: Changing the name works, but does not change the message of the SMS. The name must be set during sensor registration.
you can re-add the device. though you will loose the data but you can download it in csv
…. To change the message the trigger must be deleted and a new trigger must be created.
If you just delete and setup a new trigger, you can keep the data…. 
thanks for finding the solution.