o2.de/ersatz-sim-aktivieren
I have followed the instructions for the activation but I am keep receiving the following message.
My SIM number is XXXXX
Please let me know about the activation.
Die Aktivierung konnte leider nicht durchgeführt werden. Bitte versuchen Sie es später erneut oder wenden Sie sich an die Hotline.
Edit o2_Antje: Personal Data removed und relocated to Englisch Community
Hi
Welcome to our o2 Community.
Do you still need assistance or did you find a way to activate your simcard?
Best regards Matze
Hello, i try to activate my sim card but doesn’t work
Edit: persönliche Daten aus dem Screen gelöscht, 11.05.2023, 12.18 Uhr, o2_Micha
Hello
thanks for using the community to get in to touch with us. 
Activating a new sim card is not always easy as it should be. Were you able to activate it in the meantime, or do you still need further support?
kindly regards
Michael
Yes i still need it .
Hello
unfortunately, we can not activate the SIM card here. In order to help you, please let us have a few more information:
Is it a prepaid SIM? Then please have a look here: Register prepaid sim card | O₂ Community (o2online.de)
Or have you made a contract or is it an additional SIM (multicard))? In order to check the status of your card, you can also contact our English Hotline. They can activate the card for you.
Best regards
Giulia
Enter your E-mail address. We'll send you an e-mail with instructions to reset your password.
