dude no you guys aren't understandint what i am saying

there was a ad that said i could get a FREE TRIAL ISSUE OR THE FIRST ISSUE OF THE NEW MAGAZINE by just mailing in this postcard, so i did and i got the issue, then they sent me invoices or bills saying i needed to pay money even though im suppose to get the issue for free, so i was asking is this invoice thing something they send to try to make u subscribe and pay, because my brother told me don't pay and u won't get any more issues, i don't want any more i'm just worried about if i really owe them anything and i might get in trouble even though i shouldn't be in trouble