A complaint that charges or associated terms and conditions are unreasonable may be made by a shipper who is subject to those charges or conditions. The Agency has the power to combine two or more complaints and deal with them as a single proceeding. Since the application of the ancillary charge or condition to other shippers is one of the factors the Agency must consider in making its decision, there is a good chance that shippers who share similar concerns with respect to the same tariff provision will be able to persuade the Agency to combine their complaints. Alternatively, other shippers who have an interest in the matter may apply to the Agency to participate as interveners.