You best calling the number with 150 at the end as you will get though a little quicker and may get someone from the UK. Last twice I have gotten someone from the Newcastle area on the phone.
Although live chat online is fine and can sometimes help. Its at times better to phone but even then it can be a hit or miss.
From reading this thread I speculate the following may have occurred.
Your existing old style Entertainment package was continued the Hd/4k addon quoted originally seems to be not at the current standard rate (£6) that would be applied to a new package.
When you later contacted BT about NETFLIX inclusion it looks like BT may have stopped the old style Entertainment package which would have also automatically ceased any addons (eg the HD) that were attached to the original package. Looks like they may have then swapped you to the new Entertainment package with NetFlix basic but without adding any addons (ie HD).