Can I block a fax number?

Is it possible to block a fax number? I receive anywhere from two to twenty a day. We are receiving order confirmations from a vendor and have asked them to stop numerous times. They transitioned to a new program and they can not figure out where the box is to uncheck this oition. They said it’s an anomaly because they can not figure it out. Please advise how to block this fax number from incoming faxes. Thank you