Mont. Code Ann. § 28-1-1104
Extinction when directions of creditor followed
28-1-1104 . Extinction when directions of creditor followed. If a creditor or any one of two or more joint creditors at any time directs the debtor to perform the debtor's obligations in a particular manner, the obligation is extinguished by performance in that manner even though the creditor does not receive the benefit of the performance.