AT&T obviously is helping the U.S. government in its mass surveillance operations. The company claims that divulging such spying would almost certainly be classified by the U.S. government. This comes despite leaks that suggest a close relationship with the telecoms industry and federal intelligence agencies.
AT&T said it complies with government data requests “only to the extent required by law.”
Details may be found in an article by Zack Whittaker in the ZDnet web site at: https://zd.net/2CdF0ii.
Spying on your cell phone communications by anyone can be thwarted by use of encryption. However, securely encrypting cell phones is a more complex subject than encrypting normal web surfing. Both parties in a telephone conversation need to be using encrypted telephones or apps that include encrypted voice conversations over paths that don’t use normal telephone circuits.
For information on encrypted telephones, see https://duckduckgo.com/?q=blackphones&t=h_&ia=web.
For encrypted voice calls that are placed over the World Wide Web (not over telephone lines), see my earlier articles about Signal at: https://duckduckgo.com/?q=site%3Aprivacyblog.com+signal&t=h_&ia=web.