Call claiming to be Verizon. I am dubious as the name they had associated with the number was no one I've ever heard of, and I have had this number for a year...If it were actually Verizon, they would have called before now.
Verizon collections. Called 3 times in 5 minutes, then sent a text message. Relentless pain in the rears, but if the bill is paid on time they wouldn't be calling.