Sonys Press conference from MWC took place end of February
If you missed it you can watch it here.
Please join the discussion here and share your thoughts on what was anounced here.
MWC 2019 discussion.
I have translated your question to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you.
Based on the error message that you receive, have you tried contacting your operator and asked them if your subscription supports call waiting? Sometimes it has to be activated manually by the operator.
If you can borrow a different SIM card, preferably from a different operator from a friend, colleague or family member that would be great, so we can see if this only occurs with your SIM card or your operator.