The Deciates were a Ligurian

Ligures

The Ligures were an ancient people who gave their name to Liguria, a region of north-western Italy.-Classical sources:...

 tribe in the first few centuries BC. They lived in the Antibes

Antibes

Antibes is a resort town in the Alpes-Maritimes department in southeastern France.It lies on the Mediterranean in the Côte d'Azur, located between Cannes and Nice. The town of Juan-les-Pins is within the commune of Antibes...

 area of what is now France, west of the river Var

Var River

The Var is a river located in the southeast of France. The name Var originates from the Ligurian word for waterway.The Var flows through the Alpes-Maritimes département for most of its length, with a short stretch in the Alpes-de-Haute-Provence département...

 (Smith, entry on Deciátes; Cosson, pp.20-23). The border with the Ligurian Oxybii

Oxybii

The Oxybii were a Ligurian tribe living on the Mediterranean coast of France near Massallia. The border with the Ligurian Deciates being to the west of Antipolis and east of Forum Julii ....

 (Ὀξύβιοι) being to the west of Antipolis

Antibes

Antibes is a resort town in the Alpes-Maritimes department in southeastern France.It lies on the Mediterranean in the Côte d'Azur, located between Cannes and Nice. The town of Juan-les-Pins is within the commune of Antibes...

 and east of Forum Julii

Fréjus

Fréjus is a commune in the Var department in the Provence-Alpes-Côte d'Azur region in southeastern France.It neighbours Saint-Raphaël, effectively forming one town...

(Smith, entry on Oxybii). The Deciates had a town in the area, oppidum Deciatum but this was not Antibes itself (Pliny the Elder, Chorographia, 2.69):

In litoribus aliquot sunt cum aliquis nominibus loca: ceterum rarae urbes quia rari portus, et omnis plaga austro atque africo exposita est. Nicaea tangit Alpes, tangit oppidum Deciatum, tangit Antipolis.