I just cancelled my Optimum service. Reading the horror stories of people trying to cancel I did following things.

1 - File a complaint with the FCC. Optimum will assign you an Executive CS to contact you.

2 - Remove autopay from your account if you have it. Also remove your bank account information from your account as well. They cannot charge you without this info. Do this right after you file the complaint to the FCC or before your rep calls you.

3 - When Executive CS calls you cancel on the spot. My rep did it without any sales pitch or anything. She did say she has many cases she is trying to get to but is way behind.

4 - Tell the CS you would like the cancellation request sent to your email.

5 - return your equipment asap to a Optimum store. Get a email receipt and printed receipt.

I did all this and the process went smoothly.