I can’t see your Blizzard correspondence, but I will hazard a guess they did not tell you that you were banned for healing Mythics. They would have only told you that your account was flagged for third party software/cheating/botting/automation. Something like that.
Blizzard has NEVER intended the live chat or phone to be for Appeals. That was always supposed to go through tickets. Now, did people abuse the live systems? Yes. Now they don’t have them anymore.
The broken English “dig” tells me you are not being honest, or you got someone on a bad day. Blizzard CS is not outsourced. It is located in Austin, TX for the US, and Cork, Ireland for the EU. They are native English speakers. Yes, you WILL get a template answer. They have a set of them that are approved by the powers that be to ensure everyone gets the same answer legally. It is either overturned with an apology and game time, or upheld.
You can appeal until they tell you that they will penalize your Bnet for further Appeal tickets on that topic.
Read this post here I did yesterday with a huge explainer on ban waves and penalties. It explains a lot about how false positives are sorted and handled in case that might apply to you.
I just learned about this costume toy in another thread and I can not resist!