Paying for a service i have not used for 24 months

in the year 2013, i had taken up a data contract with MTN for R149.99, to date i have not used a single kilobite of data Yet MTN have consistantly deducted my account and continue to do so. the reason for not using the data is because the device given to me does not pick up any network in my Area (lombardy east,jhb) this cant be my fault, surely ? i had disputed this so many times and have now lost count. i have continued to pay MTN on a monthly basis as i wish not to be black listed. i feel that i am a victim to something MTN are brushing under the carpet, they cant give me answer/solution. so i continue to pay for something i have not used in 24 months, 149.99 X 24 = 3599.99 a lot of money for nothing. and just so you know, i personally had 3 contracts with you and got 4 family members to join your group. if MTN can tell me that i am a **** and that i did infact use their data, i will admit defeat and continue to pay. (this i challenge you)