Supervisor attitude and charged for no service

i had a contract with MTN which ended on the 22 May, went to one of their branch and was told i could not cancel it as their head office was on strike. They provided me with a 808 number which i kept calling but no one answered the phones, My contract was converted without my consent in which they still gave me airtime on the 14th June and debited my account on the 20th June for that airtime. I finally got hold of them on the 15th July after they credited me with airtime on the 14th July, which they took their airtime back immediately after the conversation with their consultant, to my surprise they have debited my account with R255 again and their superviser refuse to credit me back