Mont. Code Ann. § 27-18-407

All persons having in their possession or under their control any credits or other personal property belonging to the defendant or owing any debts to the defendant at the time of service upon them of a copy of the writ and notice must be, unless the property is delivered or transferred or the debts are paid to the sheriff, liable to the plaintiff for the amount of the credits, property, or debts until the attachment is discharged or any judgment recovered by the plaintiff is satisfied.