Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
Have you actually used the appeal procedure in a formal way?
As you have already found out dealing with the CMS by phone is a pointless exercise.
It appears that they have treated your contacts as a request for a re-assessment rather than as an appeal
This means that you are technically out of time for an appeal BUT I believe that you can call this exceptional circumstances!
You can find the process here
However always deal with them in writing - and keep copies.
If they phone you - follow it up with a letter setting out what they said.!
As well as appealing ALSO make a formal complaint about the way your have been dealt with since the erroneous assessment was made.
I hope that this is of assistance - please ask if you need further details
Have you not also appealed?