On the Change of Saint Paul's Name from Saul to Paul

About ten out of ten comments found online about how Paul's name switched from Saul to Paul state that Paul was his Roman name from birth. That may be, but why the switch then, in Paphos? In the Aramaic New Testament, translated by Victor Alexander, Acts 13:8-9 (footnotes added) reads:

He then stood up against them, this magician Barsum, whose name translates Alymus* (footnote: Lit. Aramaic name retained: "Sorcerer"), because he wished to get the proconsul off the faith. Saul however, who is called Paulus* (footnote: Lit. Aramaic name retained: "Paul" in English. "Sorcerer," Alymus and "undoer of sorcery," Paulus) became filled with the Holy Spirit and stared at him.

Even if Paul's Roman name was Paul from birth, perhaps his Aramaic nickname, undoer-of-sorcery (think something like "Saulus the Paulus") became his moniker from that time forward, as he desired to live in that spirit.
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Edit: From Abarim Publications, Paul : Meaning: Small, Cessation, Stopper. Etymology: From the Greek verb παυω (pauo), to stop, and Latin adjective paulus, little or small. "Will you not cease (παυω, pauo, see below) to make crooked the straight ways of the Lord?"

Edit: Some suggest that Saul adopted the name of the proconsul, Sergius Paulus. He adopted the name of Eashoa: the One Who Makes Sorcery To Cease