According to Livy (40, 43, 1), in 180 B.C. the inhabitants of Cumae asked Rome’s permission to speak Latin in public assemblies and to make sales in Latin (Cumanis eo anno petentibus permissum ut publice Latine loquerentur et … Latine vendendi ius esset). This event unmistakably shows that in this period the Cuman aristocracy was bilingual (or trilingual, since Cumae was originally a Greek colony, later conquered by the Oscan-speaking Samnites), because their request to conduct some business in Latin can only be explained if we assume that this language was well known among the members of the upper class.
There is no evidence that the Romans intended to eliminate the native language, Oscan, because the iniziative was taken by the inhabitants of Cumae themselves, who recognised the prestige of Latin to the extent that they found it advantageous to use it in public and purposely wanted to inform the Romans of their decision. This means that in the 2nd century B.C., long before the outbreak of the Social War, the Oscan-speaking aristocrats, who were becoming familiar with Latin, were trying to win the favour of the Romans by making a request that was not prescribed by the law (for further details see James Noel Adams, Bilingualism and the Latin language, 2003).