Why do I keep getting messages thanking me for activating visual voice mail

[NickJH]

I have getting these messages roughly weekly since the summer. How do I stop them? Or, at least, get O2 to stop sending them?

[jonsie]

Try turning off visual voicemail in the phone app settings

Guide: How to find help & contact O2 

[NickJH]

So I have to disable the service to stop O2 spamming me?