Why are so many people unable to extend ringtime?

Why cant i extend ringtime?

Grahams2026 try dialing this enter this code: **61*121*10*SS# to extend your ring time. Let me know how you get on.

Tried this code several times, also turned off voicemail but my Poco f9 ultra still only rings for 15 seconds. So many having same problem. Lebara must have a fix surely.

To extend the ring time before incoming calls go to voicemail on Lebara, enter a specific dialer code.
How to Extend Ring Time
Open your phone’s Phone / Dialer app.
Enter the following code, replacing XX with the desired duration in seconds (must be 5, 10, 15, 20, 25, or 30 seconds):
**61*121*11*XX#
Example for maximum ring time (30 seconds):
**61*121*11*30#
Press the Call / Dial button. You will see a confirmation message on screen indicating call forwarding updated.
Useful Status Codes
Check current ring time: Dial *#61# and press Call.
Turn off voicemail completely: Dial 1210 and press Call. (This makes your phone ring indefinitely until the caller hangs up).
Turn voicemail back on: Dial 1211 and press Call.
Troubleshooting
iPhone Users (iOS 17 or later): If the code returns an error or says successful but doesn't change the time, turn off Live Voicemail. Go to Settings > Phone > Live Voicemail and toggle it Off, then run the code again.
Wi-Fi Calling: If the code fails, turn off Wi-Fi and Wi-Fi Calling temporarily in your settings, dial the code using standard mobile signal, and then turn Wi-Fi back on.