Poor service, incorrect billing and *********** staff

I have recently upgraded from ADSL to FIBRE and was assured that there are no penalties (how can there be right??). At month end I received an invoice which was 300% my normal bill. The reason for the overcharge was shown as a "PENALTY". After logging an inquiry and after 18 days later I get no response. I spoke to at least 5 agents and 1 team leader who were all useless as my query is still not resolved.