Techniques are presented that ensure Quality of Service (QoS) for Wi-Fi® calling and other Internet Media Services (IMS) when a user connects from a carrier-operated public Wi-Fi network to an IMS. A first packet including a domain name system (DNS) request received from a wireless mobile device via an access point is intercepted at a networking device. A network address of a collocated gateway device associated with the networking device is sent to the wireless mobile device in response to the DNS request. A second packet is received from the wireless mobile device including the network address of the collocated gateway to establish a network communication via the collocated gateway device. First QoS parameters associated with the network communication are received from the collocated gateway device and a notification message is sent to the access point, the notification message including the first QoS parameters.