HP officejet all-in-one...keeps saying pho...

The very first thing to check with a fax machine is that the line itself is OK. The possibilities are much greater that there is a problem with the LINE and not the HP itself.
Hook up a regular telephone to the fax line, disconnecting anything else that may be on the line. If the telephone doesn't have a dial tone, call the phone company. If you DO have a dial tone, then maker sure that the phone line is connected to the correct port on the HP. There are two, usually. One is for the LINE and the other is for an EXTENSION (a phone that is daisy chained off the fax machine). If you have the LINE connected to the EXT port, it may give you this error.
If you have multiple items connected to the same phone line, try removing all of them but one regular phone, and see if you have a dial tone. If so, add the other items back, checking for a dial tone after each one. If one of them causes a lack of dial tone, replace or repair it.

The phone company may tell you that the problem lies in your inside wiring. I have seen that before. You can take your phone out to the telephone service box on the outside of the building. These usually have regular phone jacks in them. Disconnect the jack wire that runs into your house, and connect the regular telephone into the box itself. If you have a dial tone, then there is indeed a problem with the wiring in your building.