Missing 'Extra Volume' button during in call on Note 8

[jonspittle]

As the title states, I seem to be missing the 'Extra Volume' button that I used to have on my S8, is this firmware specific do you know? My S8 like my Note 8 was purchased directly from Vodafone.

This is what it should look like https://i.ytimg.com/vi/ky7Mcz68V5o/maxresdefault.jpg however when I make a call it briefly appears and then disappears and it's replaced with 'Call+'

I'm not sure if the 'Call+' is the cause, I do have Advanced Calling & Messaging disabled, as never found it to be useful, would this need to be completely removed?

[jonspittle]

Had a few people on another network (EE) confirm they have the extra volume button.

Would be nice to totally remove the Call + and Messaging + manually but it looks like it's built into the Vodafone firmware as there are no apps to actually uninstall and I have the option disabled within the settings. 

[jonspittle]

Just providing an update, strangely I now have the 'Extra Volume' button back on my phone which has appeared this morning, now I can only assume it's appeared since my sim swap.

Long story but I've recently moved my main number from Vodafone PAYM to Vodafone PAYG and back to Vodafone PAYM (replacing my 2nd line number) and after all this, I now have the 'Extra Volume' button!

I haven't had any updates either, bizarre!!