Why does my cell phone show an erroneous ID ONLY on MY land line?

When I use my cell (AT&T) to call my land line (Comcast), my cell has recently started showing up as "INLAND EMPIRE" on my land line Caller ID. Cell registers properly (my name) on all other phones that I have tried. AT&T, after running INOC test, says all is fine (NOT!) and problem has to be Comcast. Comcast sees no problem (Philippine tech support) from their end and says problem has to be AT&T. Any suggestions as to who is responsible and how to fix?