There is no difference between a fax line and a voice line.
There are many companies that send out faxes to get business. This is no different than junk snail mail.
I received 2 calls just minutes apart from this number to my cell phone (which used to be my land line). Not surprising. If it tries once and can't get through, it will try again. Just like when I used to send a fax and it wouldn't work. Lots of people have all-in-one printers that have a fax connected to their voice line. There is no magic here! Don't get so annoyed about things. Your blood pressure will rise and cause heart problems.
They are in violation of the FTC. I have found the person liable for their domain. Administrative Contact, Technical Contact:
Claybrook, Damian
ATTN NETPROWA.COM
care of Network Solutions
PO Box 459
Drums, PA 18222
US
570-708-8780
Please call them and inform them that Netrowa is in violations of several federal laws. I have blocked their number numerous times and they call under a new number. Send in a complaint to your attorney general. I would not put my number in their website due to they will either sell it or this is an identity theft issue. I have called the number above and informed them that their client is breaking several federal laws. Do not be a victim, take action so that we can get these guys.