Bad service I want to cancel the contract

Please assist me I need help I got a contract phone from afrizon last week and I want to cancel the contract before 14 days and I am not able to do that as I can't get hold of them. They told me I will get 20 gig data and R200 airtime but as I opened my phone at was activated on Friday the 10 June the was 6 gig and most of the data is used and I was told that I will pay R200 a month but now I am looking at the statement it has not been seven days I am owing R470 I don't understand and I want to cancel but not able to get threw company they're contact numbers are *** Theses people are unprofessional at all and I will cancel their debit order And I know that this will have a negative impact on my credit record