Voicemail notification

Just switched to Smarty SIM, porting my number over from 02. Set up voicemail greeting etc and deleted old messages but the red dot on the bottom RH corner of the app says I have a voicemail message waiting. I don't. I have got rid of the other badges on my iphone but the Smarty red dot remains. Other posts from at least 2 years ago complain of the same issue. Still not resolved it seems. 🤷🏼‍♀️