My solutions: Get a free toll-free fax number from Faxbetter.com. One has to receive a fax every week to keep it active. My backup is a free fax number from Efax.
Although I can occasionally send faxes via Voipo, I use either its outbound fax service or one of multiple free fax providers. Most free providers allow two faxes per day, but very few handle files other than .doc/.docx or .pdf. I need to fax a .xls file daily.