Voicemail not deactivating

Just wondering if anyone has had this issue. Recently moved to Smarty from EE now that Wi-Fi calling is available and which is the only option for me on any network at my address. I never use voicemail and found that the default position was that my phone would ring about 5 times and then divert to voicemail. 
Contacted smarty via live chat and so far have chatted with 4 different people as, despite being told voicemail has been deactivated, the ONLY thing which has been deactivated is my access to it. I am still getting voicemail notifications which I now can’t access and if anyone calls the phone diverts as before. I had been advised to 

1.Switch off phone, remove SIM , wait 3 mins -try again

2.Call ##002# - I get confirmation of deactivation but line still diverting

I have left this matter to be “resolved” by their back office team as no one appears to know why this is happening. I am and always have been in the UK since I started with Smarty. I keep getting a response from Smarty to say voicemail has been deactivated but it hasn’t. I’ve suggested someone from the caring’s my number to see what they get but as customer support appears to be offshore unsurprisingly no one ever takes me up on that option. 3days on I’m still awaiting a promised email to say this matter has been resolved