MTN is robbing me ,Why should I pay for data bundles on the blocked simcard ????

I took data-bundles contract with MTN ,the beginning of 2020.Then Covid-19 happened I lost my job and I managed to pay at least for the 1st 6 Months then I ran out cash .The 7th Month MTN terminated the service but i am told that I have to pay the money that I am owing for the 18 Months that I did not pay and did not receive any service from them. They closed the data immediately so why I must now pay for the months that I did not receive any data on ?????