Numbers 22:20 And God came unto Balaam at night, and said unto him, If the men come to call thee, rise up, and go with them; but yet the word which I shall say unto thee, that shalt thou do. 21 And Balaam rose up in the morning, and saddled his ass, and went with the princes of Moab.
It is reasonable to conclude that Balaam ignored the caveat ‘If the men come to call thee’.
Balaam was covetousness and in his eagerness to go and earn the money he did not wait to see if the men would come to call him. In v21 he just saddled his ass and went with them.
Peter and Jude highlight his problem:
2 Peter 2:15 Which have forsaken the right way, and are gone astray, following the way of Balaam the son of Bosor, who loved the wages of unrighteousness
Jude 1:11 Woe unto them! for they have gone in the way of Cain, and ran greedily after the error of Balaam for reward...
We will never know whether the princes intended to call for him in the morning to have a final try at persuasion before returning to Balak.
I hope you have found this helpful.
May God bless you,