why am i being called by this number and a person says nothing and will hang up if i ask them a question

Air Duct Cleaning Services calls every other day. Been getting these calls for months. Finally got fed up and booked for them to come. Gonna take photos of their licence plates and get some sort of documentation. Going after these b*****ds myself 'cause the CRTC and BBB are USELESS!!!!!

It's a duct cleaning service and I have asked them 5 times now not to call back and they always do.  They called on Saturday and I told them not to call back and then they  just called now 2 days later.  I'm on the DO NOT CALL LIST!!!!

And when you call back it says to enter an extension number

Air Duct Cleaning Services calls every other day. Been getting these calls for months. Finally got fed up and booked for them to come. Gonna take photos of their licence plates and get some sort of documentation. Going after these bastards myself 'cause the CRTC and BBB are USELESS!!!!!