IFRS 15: Agent principal relationship identification

Hi Good afternoon!! I have a question on agent and principal relation identification under new IFRS 15. For example, Parent Company-Company A has an agreement with Company B (Subsidiary Company) under which Company B has to provide services to Company A. Company A is situated in Netherland whereas Company B is situated in Bangladesh. Company B provides maintenance services to Company A’s customers in Bangladesh. Company B does not have any contract or agreement with Company A’s customer. If any spare parts are required for giving services to Company A’s customer, then Company A provides the spare parts. Company B is given cost + 15% mark up for providing services to company A’s customer by Company A. Please help me to understand, whether Company B is acting as an agent of Company A or not. Thanks! Nayeem