Succeeding the late Demetrius Vicsadoli, De Surdis was appointed provost of Kalocsa by the newly-elected archbishop Denis Lackfi in 1351, who also sent him to Avignon to the court of Pope Clement VI for his pallium.
De Surdis resided in the papal court for a year, because the pope conducted a lengthy investigation in connection with the regular election of Lackfi before its confirmation.
[1] Louis I of Hungary sent his envoy John de Surdis to Bernabò Visconti, Lord of Milan in 1360 to persuade him to abandon the siege of Bologna.
De Surdis has not achieved success; upon the request of Pope Innocent VI, Louis sent Hungarian troops to relieve the papal city.
When John de Surdis again visited Avignon still in that year, he assured the pope that Louis I, as only monarch, will provide Hungarian troops to a military campaign against the Ottoman Empire, when Peter I of Cyprus attempted to persuade a dozen European monarchs to join Urban's planned crusade.
[3] While visiting the papal court at Avignon, de Surdis also submitted the church affairs of the Diocese of Vác; for instance, he wanted to procure the church tax liability of those pagan Cumans, who lived in the territory of his bishopric, but the pope did not support him in this effort because of Louis' opposition for pragmatic and military reasons.
Alongside Judge royal Nicholas Szécsi and Cato, provost of Dömös; he sought the support of Pope Urban in the question of legitimacy of Louis I to claim the Polish throne in 1369.
When the king's distant cousin Charles of Durazzo was created Duke of Slavonia in 1371, de Surdis acted as governor of the province on his behalf.
[2][9] Following the death of Coloman (otherwise the late King Charles' illegitimate son), John de Surdis was elected Bishop of Győr sometime around May 1375.