Hi @Alma1, let me see if I can help out here.
Have you been experiencing this for a long time or has it just started happening? Also, have you been able to try other headsets to see if the phone works better with another headset?
Another thing that you can try is to reboot your phone in safe mode to see if you get the same error message there. Safe mode is a troubleshooting mode where all apps downloaded from Play Store is temporarily deactivated. That way you can see if this behaviour is caused by a downloaded app or not. For more information on safe mode and how to use it, click here.
If the same error message occurs in safe mode, my suggestion is to try to repair the software using a computer and Xperia Companion. Keep in mind though that a software repair will erase all user data from the phone, so make sure to do a backup of your user data before the repair.
If none of these measures manages to improve the functionality of the headphone jack, I believe that the best thing to do is to have the phone physically examined and repaired. In that case, please get in contact with your local support team, they should be able to arrange for the phone to be sent to an authorized service center as well as answer questions regarding local warranty and consumer laws.
Let me know how it goes!
