There are more than 12 cities!
Malbim: It says "u'Faga b'Dabeshes", but it was not in [Zevulun's border]. Davras was of Yisachar, and Gei Yiftach Kel is not a city. 1
Malbim (13) said that ha'Ne'ah is not in Zevulun, and that Kislos Tavor is in Zevulun (22). He holds that the latter is not a city. Presumably, he holds like Rashi (12) that it is on the slope of Har Tavor. (PF)