FBI and CISA officials added it was impossible to predict when telecom companies would be safe from cyber attackers.
The hacking campaign nicknamed Salt Typhoon by Microsoft is one of intelligence compromises in US history and is not been fully remediated.
Officials said China hacked AT&T Verizon and Lumen Technologies to spy on consumers.
Amid unprecedented cyberattack on telecom companies like AT&T and Verizon US officials have said that Americans use encrypted messaging apps to ensure their communication stay hidden from hackers.
In the call Tuesday two officials senior FBI official who asked not to be named and Jeff Greene assistant director for cybersecurity and Infrastructure Security Agency both recommended using encrypted text apps to Americans who desire to minimize the chances of China intercepting their communications.
A spokesperson for Chinese Embassy in Washington denied the country was behind hacking campaign China firmly opposes and combats all kinds of cyber attacks.
One type has been call records or metadata showing numbers that phones called and when The hackers focused on record around the Washington DC area and FBI does not plan to alert people whose phone metadata was accessed.
Privacy advocates have advocated using end to end encrypted apps. Signals and Whatsapp automatically implement end to end encryption in messages and calls.
Google Messages and iMessage can encrypt calls and texts end to end.
The third has been systems that telecom companies use in compliance with Communications Assistance for Law Enforcement Act which permits law enforcement and intelligence agencies with court orders to track people communications.
CALEA systems can include classified court orders from Foreign Intelligence Surveillance Court which processes US intelligence court orders.
The hacking campaign was first publicly disclosed in lead up to election the US believes it was not attempt to sway results.
