Bad service

I have been making payment for the past 6 months consecutively last year but there hasn’t been any progress on my account , I would still get charged for SMS or calls that I have never even received , till I stopped making payment in January because it did not make sense as to why I pay every month but the amount remains the same .Today I called the company and asked the final amount to settle my account and the discount , I had already logged in to their self service portal and the lady on the call spoke a different amount than the one I am seeing on the statement I saw online .I told her I am not going to agree to a price that I don’t know anything about and can my issue be escalated to the manager , I then asked how soon can I get feedback and she said she doesn’t know which manager is working and when I’ll get feedback .When I tried to voice out also about my previous payments and charges I do not know about , her tone changed .It is really unfair that I would be forced to an amount I know nothing about and it’s not matching what is on their system