(I presume this is only an extension of the main number.) I stupidly signed up with a travel group. It's changed names a few times so I don't even remember its current name, but it's something like "Travel Options Group." I didn't use all of the "free" travel I paid for so every time they changed owners they would call and say I had to "re-activate" my account. I did that once and still get the calls. They've called at work, at home, and even on my cell (which is how I got a trackable number since I don't have caller ID on my home/work phone). I told each person who calls to take me off their calling/marketing/whatever list and they just hang up on me and someone else calls. They usually call every 3 months and call about 3-4 times within 1 week and then go silent for 3 months.

Travel Options picked up the phone.  Won't stop calling.