Multi organisation customer with one ICT team

I have a customer consisting of: Headquarter, Hotels, Campings and Retails. Hotels has 10 hotels and resorts, Campings has 6 campings and Retails has store and 20+ retail shops. We are network support for all of them, 100+switches, few firewalls, 20+ routers, huge WiFi, radio links fiber optics.... They have one common ICT team of manager and six technicians, who raise requests and communicate with us for problems we are responsible for. Would you help us how to organize that client? Every person from ICT team can raise the ticket for headquarter, any hotel, any camping or retail shop and access the customer portal, view the history and resolution for every object.
Till now, those units are Accounts and every hotel and camping and so on are Contacts but that does not suit us(them) for Customer portal access.