Virgil Johnson and Virgil Johnson Trucking v. Associated Milk Producers, Inc., 886 N.W.2d 384

AMPI (a dairy cooperative) and Virgil Johnson (independent hauler) had an oral, indefinite-duration hauling agreement paying a base rate plus a $100 "trip fee" for certain deliveries.
The parties treated the agreement as terminable at will; no durational assurances were made and both acknowledged ability to stop performance.
In July 2013 AMPI notified Johnson it would phase out the $100 trip fee over several months and then eliminate it; Johnson protested in writing but acknowledged understanding the change.
Johnson continued to haul milk, invoiced AMPI for the $100 trip fee (and later added interest), while AMPI paid under the new schedule and repeatedly told Johnson the trip fee would end.
Johnson sued for breach of contract, promissory estoppel, and unjust enrichment; the district court granted summary judgment for AMPI, concluding an at-will contract can be modified prospectively with reasonable notice and accepted by continued performance.
The court of appeals reversed; the Iowa Supreme Court granted further review and vacated the court of appeals, affirming summary judgment for AMPI.

Issue	Plaintiff's Argument (Johnson)	Defendant's Argument (AMPI)	Held
Which rule governs modification of the parties' agreement (at-will vs. mutual-assent/consideration rule)?	The July 31 notice attempted to modify an existing bilateral contract and required mutual assent and consideration.	The agreement was at-will; AMPI could terminate/modify prospectively on reasonable notice and offer new terms.	At-will rule governs: terminable-at-will contracts may be modified prospectively by one party upon reasonable notice.
Whether Johnson accepted AMPI's new terms and whether summary judgment was proper	Johnson protested and therefore did not assent; factual disputes over acceptance preclude summary judgment.	Johnson knew of the change yet continued performance and accepted the new terms as a matter of law; summary judgment appropriate.	Johnson's continued performance with knowledge of the change constituted acceptance as a matter of law; summary judgment for AMPI affirmed.

Davenport Osteopathic Hosp. Ass'n v. Hosp. Serv., Inc., 261 Iowa 247, 154 N.W.2d 153 (Iowa 1967) (modification of an existing contract with an unused termination clause requires mutual assent; continued performance while protesting did not constitute acceptance)
Cannon v. Nat'l By-Products, Inc., 422 N.W.2d 638 (Iowa 1988) (at-will contracts may be rescinded and a new contract formed without independent consideration)
Moody v. Bogue, 310 N.W.2d 655 (Iowa Ct. App. 1981) (notice that continued employment would be subject to new conditions constituted effective modification; continued work is acceptance)
Shelby Cty. Cookers, L.L.C. v. Util. Consultants Int'l, Inc., 857 N.W.2d 186 (Iowa 2014) (services contracts indefinite in duration are commonly terminable at will)
Jones v. Univ. of Iowa, 836 N.W.2d 127 (Iowa 2013) (describing at-will contractual relationships)
Willets v. City of Creston, 433 N.W.2d 58 (Iowa Ct. App. 1988) (employee's continued work after notice of changed terms is acceptance as a matter of law)