Time phone rings before going to voicemail

[PHEZ]

O2 have tried UNSUCCESSFULLY 3 times to increase my ring time from 15seconds to 25 seconds.

They keep sending me **61*901*11*25#

but all I get is “an invalid MMI code.  And it also deactivates my voicemail!

i have a Samsung S22+

Can anyone help?

[Enlli · Accepted solution]

Seen this before with Samsung. One fix is to make sure both WiFi and 4G are turned off.

I've known cases where this has worked, but sadly cases where it hasn't.

Still, worth a shot