In many countries, initiating a denial-of-service attack on a communication device violates federal cyber laws.
Using or hosting tools under the "call bomber com" umbrella exposes individuals to severe personal, operational, and legal hazards. 1. Digital Harassment and Cyber Bullying
Modern Android and iOS devices have "Silence Unknown Callers" or "Spam Protection" features that can filter out a large portion of automated traffic.
Do not text the attacker. Do not answer the calls. The attacker is likely watching a counter on a browser tab. If you react, they feel powerful and will extend the attack.