Best chance is to reverse the situation give their number to all the solicitors you can find and let them get tons of scam and junk calls making their whole industry fighting with each other.
The more you threaten them, the more they will call. These are criminals making the calls and they have NO intention of stopping. Go to this link for a detailed discussion of call blocking devices.
http://800notes.com/forum/ta-5d4e343675a5629/call-blocking-devices
This is a Canadian Pharmacy apparently based in India (according to accent) Have asked that they not call - I don't use pharmacy outside of U.S. and have no need for medication "viagee" In June I got billed for an eight (8) hour telephone call to this number (which I did not make) and Verizon would not do anything about it - it cost me almost $130 for this call. Five (5) different people at Verizon told me they knew it was fraud but there was nothing they could do and I would have to pay for it or have my service cut off. I have tried to have this number blocked but apparently the block thru Verizon is not working! This is ridiculous and the honest, paying Americans can not do a thing about this crap!