Despite being given the opportunity to receive nevuah and despite seeing the spiritual greatness of Klal Yisrael -- "mah tovu ohalecha Yaakov" -- Bilam remains unchanged as a person from the start of the parsha through its end. When the plan to curse fails, it does lead to a change of heart, a re-evaluation and reconsideration, but rather it leads to a new wicked plan and the episode of bnos Moav. The kabbalists link Bilam with Lavan; some claim they were one and the same person. Much like Lavan, who despite years of exposure to Yaakov Avinu simply goes back to being his old self, "Vayelech vayashav Lavan lmkomo," (32:1) after Yaakov's departure, so too Bilam, who, after experiencing prophecy simply goes back to being his old self, "Vayakam Bilam vayelech vayashav limkomo," (24:25) with no change in attitude or character.
The Chofetz Chaim noted the interesting fact that the entire story of Bilam's prophecy appears as one long parsha stuma in the Torah with no breaks -- something not too common. Rashi writes at the beginning of parshas Vayikra that the breaks between parshiyos served to allow Moshe time to reflect on what he was learning, to be misbonein. Even if a person is given the gift of nevuah, without hisbonenus, without taking time for contemplation to internalize the message and its meaning, the person will remain unchanged like Bilam and never grow like Moshe.