Trends' claim for defamation and breach of contract is due to go ahead in November and take 10 days.
Earlier this month, Callaghan tried to adjourn the hearing because senior lawyer, Queen's Counsel Daniel McLellan, is not available at that time because of a trial in the Cook Islands.
Justice Paul Heath, in a recent decision, did not think this was enough to justify putting the hearing off.
The right of a litigant to go to trial with their lawyer of choice must be balanced with other considerations, he said.
Trends' lawyer Kalev Crossland said the value of his client's business had been adversely affected by Callaghan's statements.
"While that contention is disputed, the possibility of additional financial harm caused by delay is a relevant consideration on an application of this type," Justice Heath said.
"As the trial is not due to commence until 21 November 2016, there is ample time for alternative counsel to be instructed. I am not persuaded that, in the circumstances of this case, Callaghan's presumptive right to counsel choice should override the desirability of a prompt decision...," the judge said.
Trends chairman David Johnson castigated Callaghan in 2014 when it released the allegedly defamatory press release.
Johnson "absolutely" denied Callaghan's allegations and said Trends met the criteria for its grant.