Worse Experience: Unable to move from By the Gig to unlimited mobile plan

I  have been trying to convert my mobile service for 2 of my phone lines from by the gig to unlimited. I spent close to 1.5 hr over the phone on 19th November and I was told the service will be migrated to unlimited but unfortunately it didn't work. 

Again spent 1.5 to 2 hrs on 21st November talking explaining the same situation and I was told service will move to unlimited but again no luck. Since I was not confident I requested email about the change which I was told will receive within 24 hrs but no luck. Was forced to call again today(22nd November), now I'm been told that it cannot happen and one of the agent not willing to look up the log and threatening to hang up.  After complaining to the supervisor she keeps me on the phone call keeps me listening to music  for 1hr 15 minutes and hung up eventually.

I feel frustrated with the state of affair and hopefully address this basic ask from the customer.

Regards,
Raj