I have followed the steps outlined https://yescrowd.optus.com.au/t5/Optus-Sport-Discussion/How-to-unsubscribe-from-Optus-Sport/m-p/4683... but I don't see a 'entertainment tab'. Therefore, I cannot unsubscribe from Optus Sport. I had similar issues last year and it is concerning that it is yet to be fixed.
It's not you Max the Optus account portal is absolute crap in my opinion and one never knows what they are going to find on any given day. You need to click on the service in question to bring up the additional tabs. You normally see all your services on the first page. In my case I click the big round data usage graph (go figure) and the additional tabs come up. If you don't see it you might be better off asking support on the live chat below if they can do it for you.
Edit: I went to take a screen capture for you and my own Optus Sports account is missing.
Thanks for pointing that out, I've updated those out of date instructions.
Weird, mine is there.