International Magazine Company can't get ahold of these people to get anything done largo, Florida

i stupidly got this, when i wanted to cancel the service i couldn't get a hold of these people.i have written them letters three times,emailed them four times (i found there email on the bbb website)and tried to call them more times than i can count.the emails and letters were returned to me saying that they are undeliverable,when i called no one picked up the phone, and then just today i got a letter in the mail saying that they are suspending my subscription and i had to call them to pay for something that i don't want.and if i don't they will take more drastic measures.i should say that when i couldn't get of them to cancel the service i call my bank and changed my bank card so they couldn't get into my account again.i would like to know how to get rid of these people.i am not going to pay them another cent of my money.