Apple is telling Congress that its iPhone location tracking is meant to improve service, not stalk customers, AP reported. The company outlined its stance in a letter released Monday by the House of Representatives. An Apple Inc. vice president, Guy Tribble, is set to testify Tuesday before a Senate subcommittee. A Google Inc. executive, Alan Davidson, is also set to testify. Congress is demanding details from smartphone companies about their tracking practices, after researchers revealed last month that iPhones and Android phones themselves were secretly keeping track of users' locations. Apple and Google say they only record the location of Wi-Fi hot spots and cell towers to improve service, and tracking can be turned off. Apple said a "bug" caused the iPhone to keep location data even when tracking was disabled.