I keep getting VOICE MAIL notifications two or three per day like I have missed calls

I have only been a Lebara customer since 4th June 2026.
I keep receiving VOICE MAIL notifications two or three times per day and sometimes while I am asleep as if I have missed a phone call, BUT I rarely received phone calls at all.
I did call someone at Lebara Customer service, they did not help stop the notifications.
I have tried using the 1210 to switch off the voicemail function, but continue to receive voice mail notifications

Dial voicemail 121 and go to your notification settings. Change your setting to one of the other options. Hang up then go back into voicemail and the notifcation settings menu again and change the option back to what it was. This should clear the stuck setting.

I have tried what you suggested a number of times, but I still received ghost voicemail notifications.
Yesterday I dialed 1210 at 13.46 and got an automated voice said "Your voicemail service has now been switched off", but I am still receiving ghost email notifications.