Problem with voicemail after porting to Sky

[Toontitan]

I ported my number from my former employer's corporate Vodafone account to my Sky account 10 weeks ago. My Sky account is an e-sim and I have no other physical sim in my phone, which is an iPhone 15 pro. 
My phone receives and makes calls perfectly, however, after setting up my voicemail (added a pin, recorded a message, disabled secondary message) my callers receive the voicemail message that I recorded whilst with my former employer, not the one I have on my Sky account. I've tried resetting my phone, reinstalled latest Sky browser settings, all to no avail. 

Does anyone have any ideas how this can be resolved? 

[63johnw]

Hi @Toontitan  have you tried setting so voicemail can't be left for a while then reactivate it ?

Voicemail can’t be switched off completely. But, to stop people leaving you voicemail messages, turn message recording mode off.

On your phone:

1. Dial 759.
2. Press 3.
3. Press 5.
4. Press 1.

[Toontitan]

Hi John, thanks for your input. 

I've tried that, left it, turned voicemail back on but callers are still getting my old message which is no longer appropriate.