No change to dialling tone to notify me of voicemail

[#1]

Hi, I don't know if it's my phone or the service but my dial tone doesn't change when I have a new message, does anyone know how to fix it please?

[#2]

Good morning hermum,
This is something that has come up a few times in the past and unfortunately, there is nothing we can do about it..
It usually happens when a customer comes from an LLU provider like talk talk or Sky.
This is because of how the equipment is set up in the exchange.
Sorry I couldn't be anymore help!!