Although courts have held that if there is partial performance under an oral modification and as a result, the doctrine of equitable estoppel would apply, such modification would have to have been agreed to by both parties. Beacon Term. Corp. v Chemprene, Inc., 75 AD2d 350, 354 [2d Dept 1980]. Additionally, for a course of performance to demonstrate mutual assent to a modification, it must be unequivocally referable to the modification. Nassau Beekman, LLC v Ann/Nassau Realty, LLC, 105 AD3d 33, 35 [1st Dept 2013].