First time poster, but registered in case my experience helps others.
If you pay for call divert and cancel it, be aware that the divert setting may continue. I found this out today, when I put my landline phone number back into service, I cancelled the number the divert was originally going to as well (a VoIP number).
When I plugged the phone back in, I was able to call out successfully, but noticed that when I called the number from my mobile, it said the number was disconnected.
I rang plus.net support, they only said that call divert had been cancelled in December 2019 and therefore the Plus.net phone number was some how being controlled by a third party (the VoIP people). That led me down a brief goose chase - always thinking that no company other than Plus.net could control the divert of phone calls? Unless they had porting access or something sounding similar - a friend was in telecoms and bored me to death with that tech talk.
I had a brain wave and went to my office, I entered the code for disabling call divert - and wouldn't you know it, that fixed it.
So the morale of the story - even if you've cancelled a service, it does not mean that it's been disabled.