They also help police catch criminals.
That's because the towers collect information about when, where and who a person calls or texts.
Police can then gather that data in bulk in what's known as tower dumping.
"Its a continuation of the erosion of our rights," said cell user Ray Bergeron.
Police made about 9,000 tower dumps last year and requested more than one million phone records according to a study by Massachusetts' democratic Senator Ed Markey.
Now Markey is proposing new legislation that would require police get a warrant before gathering phone users G.P.S. data and limit how long police can keep a caller's phone records.
Law enforcement agencies worry new limits could mean fewer crimes solved.
"We want to make sure we aren't putting up too many roadblocks for law enforcement," said Steven Jansen of the Association of Prosecuting Attorneys.
There is no reason for the police not to be able to pursue the guilty while at the same time protecting the privacy of innocent Americans," Markey said.
The debate comes as eight leading tech companies, including Apple, Google and Facebook, demand new limits to government snooping by agencies like the N.S.A.
The question now for lawmakers is where the balance should lie between privacy and safety.
In an open letter to the President and Congress tech companies argue surveillance needs to be more in their words, "proportionate to the risks."
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