Debbie:

My experience. Left MCI in the past, and yes, it took almost two months for them to recognize my abscence. However, I recently switched to sprint on 4/6 and by 4/28 I received an offer for 2k bonus miles (united, via mail) to come back. Also called MCI to make sure that "I'm gone." So this time, the most recent, it didn't take that long. My brother had to call to tell MCI he didn't want their service before he was disconnected (?). Thus, perhaps switch away and call and tell them to cancel your account.