Ackermans Fone yam complain

I have been ****med by ackermans agents.they tell us lies about cellphone contracts(Fone yam)when I signed contract they told me I was gonna pay R120 monthly for 12 months but to my surprised yesterday when I went to pay they told me mi installment is R220 monthly for that 12 months.I feel cheated and I would like to get help and make aware to others .they must tell us the truth cause this is gonna lead us to unnecessary blacklistingq