This is a type of Denial Of Service attack. You need to exhaust the resources of the victim in order to make a successful attack. The memory on a smartphone is way more than that of a Bluetooth speaker and so that attack has to be of a much larger scale even without any additional countermeasures deployed in the smartphone.
You need to check if the attack is using spoof addresses or not, if you can identify the ip address then drop them on a firewall/iptables or whatever you have. if the address are spoofed then you will need to use rate limiting, max tcp syns allowed and so on. If you cannot stop it then contact to your ISP.