Many researches for detecting feature interactions of telephony services have been discussed all over the world. But, there is no guarantee that all detected feature interactions can be resolved. In fact, services must be provided with unresolved feature interactions still remained. Consequently, a method for avoiding feature interactions at run-time is required. However, as far as the authors know, any effective solutions for avoiding feature interactions at run-time have not yet been proposed. In this article, it is clarified that even for services between which feature interactions occur, in some terminal assignments, feature interactions do not occur. Based on this fact, a method for avoiding feature interactions is proposed, where service initiation is prevented only when a terminal assignment causes feature interactions.